feat(left): add subject, test and solution for the exercise

sh/tests/left/facts

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+10 random facts
+
+- Avocados are a fruit, not a vegetable. They're technically considered a single-seeded berry, believe it or not.
+
+- The Eiffel Tower can be 15 cm taller during the summer, due to thermal expansion meaning the iron heats up, the particles gain kinetic energy and take up more space.
+
+- Trypophobia is the fear of closely-packed holes. Or more specifically, "an aversion to the sight of irregular patterns or clusters of small holes or bumps." No crumpets for them, then.
+
+- Australia is wider than the moon. The moon sits at 3400km in diameter, while Australia’s diameter from east to west is almost 4000km.
+
+- 'Mellifluous' is a sound that is pleasingly smooth and musical to hear.
+
+- The Spice Girls were originally a band called Touch. "When we first started [with the name Touch], we were pretty bland," Mel C told The Guardian in 2018. "We felt like we had to fit into a mould."
+
+- Human teeth are the only part of the body that cannot heal themselves. Teeth are coated in enamel which is not a living tissue.
+
+- It's illegal to own just one guinea pig in Switzerland. It's considered animal abuse because they're social beings and get lonely.
+
+- The Ancient Romans used to drop a piece of toast into their wine for good health - hence why we 'raise a toast'.
+
+- The heart of a shrimp is located in its head. They also have an open circulatory system, which means they have no arteries and their organs float directly in blood.

sh/tests/left_test.sh

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+#!/usr/bin/env bash
+
+# Unofficial Bash Strict Mode
+set -euo pipefail
+IFS='
+'
+script_dirS=$(cd -P "$(dirname "$BASH_SOURCE")" &>/dev/null && pwd)
+
+FILENAME="../student/left.sh"
+cd left
+
+# True if FILE exists and is a regular file
+if [ -f ${FILENAME} ]; then
+    # FILE exists and it's not empty
+    if [ -s ${FILENAME} ]; then
+        if [[ $(cat $FILENAME | grep echo | wc -l) -ne 0 ]]; then
+            echo "echo is not allowed in this exercise!"
+            exit 1
+            submitted=$(bash $FILENAME)
+            expected=$(bash ../solutions/left.sh)
+            diff <(echo "$submitted") <(echo "$expected")
+        fi
+    else
+        echo "The file exist but is empty"
+        exit 1
+    fi
+else
+    echo "File does not exist"
+    exit 1
+fi

sh/tests/solutions/left.sh

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+wc -l <facts

subjects/devops/left/README.md

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+## left
+
+### Instructions
+
+Create a file `left.sh` that will pass the content of a file `facts` to a command that will return the number of lines in that file.
+
+### Usage
+
+```console
+$./left.sh
+21
+```
+
+### Hints
+
+To pass the content of a file to a command in a shell, you can use the "<" operator followed by the name of the file. For example, to pass the content of a file named "input.txt" to the cat command, you can use the following command:
+
+`cat < input.txt`
+
+The `wc` command is a utility in Unix-like operating systems that is used to count the number of lines, words, and bytes in a file or group of files. The -l option tells wc to only print the line count for each file.
+
+For example, if you have a file called "file.txt" and you want to count the number of lines in the file, you can use the following command:
+
+`wc -l file.txt`
+
+This will print the line count for "file.txt".
+
+> You have to use Man or Google to know more about commands flags, in order to solve this exercise!
+> Google and Man will be your friends!

subjects/devops/left/facts

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+10 random facts
+
+- Avocados are a fruit, not a vegetable. They're technically considered a single-seeded berry, believe it or not.
+
+- The Eiffel Tower can be 15 cm taller during the summer, due to thermal expansion meaning the iron heats up, the particles gain kinetic energy and take up more space.
+
+- Trypophobia is the fear of closely-packed holes. Or more specifically, "an aversion to the sight of irregular patterns or clusters of small holes or bumps." No crumpets for them, then.
+
+- Australia is wider than the moon. The moon sits at 3400km in diameter, while Australia’s diameter from east to west is almost 4000km.
+
+- 'Mellifluous' is a sound that is pleasingly smooth and musical to hear.
+
+EOF
+
+- The Spice Girls were originally a band called Touch. "When we first started [with the name Touch], we were pretty bland," Mel C told The Guardian in 2018. "We felt like we had to fit into a mould."
+
+- Human teeth are the only part of the body that cannot heal themselves. Teeth are coated in enamel which is not a living tissue.
+
+- It's illegal to own just one guinea pig in Switzerland. It's considered animal abuse because they're social beings and get lonely.
+
+- The Ancient Romans used to drop a piece of toast into their wine for good health - hence why we 'raise a toast'.
+
+- The heart of a shrimp is located in its head. They also have an open circulatory system, which means they have no arteries and their organs float directly in blood.