feat: Implement API-based Transifex stats generation and CI automation

[Revisto]

This PR adds new scripts to get translation stats from Transifex using its API. It also sets up a GitHub Action to automatically update these stats in the repository.

What Changed:

1. Python Scripts for Stats (transifex):

   • Added new functions to fetch data from the Transifex API (like translation progress and contributor activity).
   • Created different "reporters" to make specific files:
     • RESOURCE.md: Shows how much of each file is translated.
     • TEAM.md: Lists contributors and their work.
     • reports/contributor_stats_YYYY_MM_DD.png: A chart showing top contributor activity.
     • README.md: Updated with the latest contributor chart and summary.
   • Added a new command generate-all-stats to main.py.
     • When you run python -m scripts.transifex.main generate-all-stats, it runs all the above reporters one by one.
     • This way, it only needs to get data from the Transifex API once for things that are used in multiple reports, making it faster.

2. GitHub Actions Workflow (.github/workflows/update-translation-stats.yml):

   • What it does: Automatically runs the generate-all-stats script.
   • When it runs:
     • Every Saturday at midnight (UTC).
     • Can also be run by hand if needed.
   • How it works:
     • Gets the latest code.
     • Sets up Python.
     • Installs the Python packages listed in requirements.txt.
     • Runs the generate-all-stats script (it uses a TRANSIFEX_API_TOKEN secret to talk to Transifex).
     • If the script changes RESOURCE.md, TEAM.md, files in reports, or README.md:
       • It sets up Git.
       • Adds the changed files.
       • Makes a commit with the message "Update translation statistics [skip ci]".
       • Pushes the changes.

Why this is good:

• Correct Stats: Uses the official Transifex API, so the information is right.
• Always Up-to-Date: The stats files in the repo will be updated automatically.
• Runs Faster: The generate-all-stats command is set up to avoid asking Transifex for the same data over and over.
• Easy to See Progress: Helps everyone see how the Persian Python docs translation is doing and who is helping.

This makes it much easier to track and show our translation work.