Add download counters script

[utarwyn]

This pull request introduces a new script to retrieve the download counts of a list of repositories from the GitHub API. The changes include adding a README file with detailed instructions and the actual script to perform the download count retrieval.

Here is an example of what the script shows:

$ ./tools/download_counters/count.sh
Repository: green-code-initiative/ecoCode-android, Download Count: 2974
Repository: green-code-initiative/creedengo-csharp-sonarqube, Download Count: 1302
Repository: green-code-initiative/creedengo-ios, Download Count: 421
Repository: green-code-initiative/creedengo-java, Download Count: 14548
Repository: green-code-initiative/creedengo-javascript, Download Count: 12767
Repository: green-code-initiative/creedengo-php, Download Count: 5529
Repository: green-code-initiative/creedengo-python, Download Count: 12370

This is a first version which can be improved to see the detail by version for example.
And I can also propose a GitHub workflow to run the script from GitHub directly. Good idea?

[dedece35]

for me, it's less system intrusive if you manage the github_token as an input parameter of the script instead of using a new system variable which can potentially be used for other usages in local machine

[dedece35]

maybe here, a lack of information to configure the personal github token, i.e. options to select for token generation (after testing your script, only "repo / public_repo" option needed)