feat(kept-promise): add hints and suggestions

subjects/devops/kept-promise/README.md

@@ -11,7 +11,7 @@ Create an asynchronous function `processInfo` in a file `kept-promise.js`. The f
 The following function can be used as an example of input function for `processInfo`:
 
 ```js
-const getImportantInfo = async _ =>
+const getImportantInfo = async () =>
   new Promise(resolve => resolve(Math.round(Math.random() * 10)))
 ```
 
@@ -24,10 +24,8 @@ The following script `main.js` can be used to test your function:
 ```js
 import processInfo from './kept-promise.js'
 
-const getImportantInfo = _ =>
-  new Promise(resolve => {
-    setTimeout(() => resolve(Math.round(Math.random() * 10)), 1000)
-  })
+const getImportantInfo = () =>
+  new Promise(resolve => resolve(Math.round(Math.random() * 10)))
 
 console.log(await processInfo(getImportantInfo))
 ```
@@ -46,7 +44,24 @@ $
 
 ### Hints
 
-- It is possible to wait for an asynchronous function with the keyword `await`. Alternatively, it can be clearer to use the method `.then`.
+- A `Promise` is a special JS object that represent the result (succes or failure) of an asynchronous operation. This special object is usually used to "wrap" asynchronous operations.
+  `Promise`s can have three different states: _pending_ - the asynchronous operation has not finished yet, _fulfilled_/_resolved_ - the asynchronous operation has finished successfully - or _rejected_ - the asynchronous operation has finished, but something went wrong. When defined from scratch, it is possible to define a `resolve` and `reject` callback function for a new `Promise` that will define the results of the success or failure of asynchronous operation happening inside the `Promise`
+
+- It is possible to wait for an asynchronous function with the keyword `await`. Alternatively, it can be clearer to use the method `.then`. Below an example of how to handle promises and, more generally, asynchronous operations.
+
+```js
+const promise1 = new Promise((resolve, reject) => {
+  resolve('Success!')
+})
+
+console.log(await promise1)
+// Expected output: "Success!"
+
+promise1.then(value => {
+  console.log(value)
+  // Expected output: "Success!"
+})
+```
 
 ### Notions
 
@@ -54,3 +69,4 @@ $
 - [await](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/await)
 - [Using promises](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Using_promises)
 - [async function](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/async_function)
+- [then](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/then)