feat(master-the-ls): add subject, test and solution for the exercise master-the-ls

sh/tests/master-the-ls_test.sh

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+#!/usr/bin/env bash
+
+# Unofficial Bash Strict Mode
+set -euo pipefail
+IFS='
+'
+
+script_dirS=$(cd -P "$(dirname "$BASH_SOURCE")" &>/dev/null && pwd)
+
+challenge() {
+    submitted=$(cd "$1" && bash "$script_dirS"/student/master-the-ls)
+    expected=$(cd "$1" && bash "$script_dirS"/solutions/master-the-ls)
+
+    diff <(echo "$submitted") <(echo "$expected")
+}
+
+challenge cl-camp1/folder1
+challenge cl-camp1/folder2

sh/tests/solutions/master-the-ls

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+#!/usr/bin/env bash
+
+ls -p -tu | tr '\n' ',' | sed 's/.$//'

subjects/master-the-ls/README.md

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+## Master the ls
+
+### Instructions
+
+Put in a file `master-the-ls`, the command line that will:
+
+- list the files and directories of the current directory.
+- Ignore the hidden files, the "." and the "..".
+- Separates the results with commas.
+- Order them by ascending order of access time (the newest first).
+- Have the directories ends with a `/`.
+
+### Hint
+
+Here are some Commands that can help you:
+
+- `tr`. Translate characters: run replacements based on single characters and character sets.For more information: https://www.gnu.org/software/coreutils/tr.
+
+  - Replace all occurrences of a character in a file, and print the result:
+    `tr {{find_character}} {{replace_character}} < {{filename}}`
+
+- `ls`. List directory contents. For more information: https://www.gnu.org/software/coreutils/ls.
+- `sed`. Edit text in a scriptable manner. You can see also: awk. For more information: https://www.gnu.org/software/sed/manual/sed.html.