What?

This PR checks:

• the missing uppercase in the beginning of the translations when the original starts with an uppercase.
• the missing lowercase in the translation when the original string starts with lowercase.

When some of these situations are found, the checker adds a warning.

See #1441.

Why?

In a lot of translations, the translators forget to start the translation with uppercase when the original string starts with uppercase or starts the translation with lowercase when the original starts with lowercase.

How?

This PR:

• Adds the alphabet used by each locale. This locale was used before the change to use regex to detect if a string starts with uppercase or lowercase. It is ok to delete the changes added in the locales/locales.php file, but it could be useful in the future, and it is a work that takes a few hours.
• Checks if the first letter of the original and the translation strings starts both with uppercase or lowercase. The check uses a regex, so only makes sense in alphabets with uppercase and lowercase (Latin, Greek, Cyrillic and Armenian).

Testing Instructions

This PR adds some tests for the new warning method. To execute it, run:

• composer test to run all tests.
• vendor/bin/phpunit --filter test_missing_uppercase_beginning to run only the new tests.

Screenshots or screencast