New Function: map and flat a nested array with `flatMap()`

[roberto-butti]

What

Add new method documentation file for a new JavaScript function in src/content/docs. The instructions about defining the file's name are documented in the CONTRIBUTING.md file.

Description

Function name: example array.flatMap() Function description: map and flat a nested array File name: example 02-array/18_array-flatmap.md

Checklist

• [ ] create the file with the proper name
• [ ] create the documentation of the function
• [ ] write example in examples directory
• [ ] execute bun run format-examples-bun or npm run format-examples
• [ ] commit and open the PR.

Must read:

• https://github.com/roberto-butti/some-drops-of-javascript/blob/main/HACKTOBERFEST.md
• https://github.com/roberto-butti/some-drops-of-javascript/blob/main/CONTRIBUTING.md