feature #40947 [Translation] Added Crowdin Translation Provider (andr…

…ii-bodnar)

This PR was squashed before being merged into the 5.3-dev branch.

Discussion
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[Translation] Added Crowdin Translation Provider

| Q             | A
| ------------- | ---
| Branch?       | 5.x
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Tickets       |  <!-- prefix each issue number with "Fix #", no need to create an issue if none exist, explain below instead -->
| License       | MIT
| Doc PR        | <!-- required for new features -->

To follow up on #38475, this PR adds [Crowdin](https://crowdin.com/) Provider.
This provider was removed a few weeks ago from the Translation Providers feature by `@welcoMattic`.

We discussed all the recent changes made on `ProviderInterface`, `TranslatorBagInterface`, and others and I already applied these changes to Crowdin Provider.

Also, this Provider is adapted to work with both [Crowdin](https://crowdin.com/) and [Crowdin Enterprise](https://crowdin.com/enterprise).

The todo list to make it ready is:
- [x] Write integration tests by mocking HTTP Responses

I will make it done before the beginning of May.

Commits
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d7fda16262 [Translation] Added Crowdin Translation Provider

Bridge/Crowdin/.gitattributes

@@ -0,0 +1,4 @@
+/Tests export-ignore
+/phpunit.xml.dist export-ignore
+/.gitattributes export-ignore
+/.gitignore export-ignore

Bridge/Crowdin/.gitignore

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+vendor/
+composer.lock
+phpunit.xml

Bridge/Crowdin/CHANGELOG.md

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+CHANGELOG
+=========
+
+5.3
+---
+
+* Create the bridge