Add scripts to allow addons from personal repos to be synchronized with Crowdin

[nvdaes]

No description provided.

[seanbudd]

it's probably better to keep these rules than dropping to NVDA's standard

[nvdaes]

Purpose

Add-on authors may wish to help translators use Crowdin, the same framework where they translate NVDA. to translate messages and documentation for maintained add-ons:

Other details

• Pot file are created/updated, and uploaded to a Crowdin project.
• The readme.md file is converted to xliff and uploaded to a Crowdin project.
• Po and xfiles are translated.
• Translated files are downloaded and processed to be copied to locale/langCode/LC_MESSAGES/nvda.po, and doc/langCode/readme.md, in the addon folder.
  Authors need to store a Crowdin token with permissions to upload files to the Crowdin project as a repository secret.

Development approach

Use the Crowdin registration repo to add scripts usable by individual add-ons in personal repos.

[nvdaes]

I've tested that all check pass using this pyproject.toml file on this PR:

nvdaes/translateNvdaAddonsWithCrowdin#11

I use precommit, CodeQL and a workflow to check that all translatable messages have comments for translators.

I'll try to use the cache action to cache some add-on metadata like its id, and also hashfiles from l10nSources (taking the value of buildVars.py), and the hasf¡hfile of the readme.md, to determine if pot and xliff files should be updated.