Add Estonian (et) translations

[0jar]

Description

Added Estonian (et) locale to translations.

Type of change

• New feature (added a non-breaking change which adds functionality)

How Has This Been Tested?

• Tested locally with a valid username
• Tested locally with an invalid username
• Ran tests with composer test
• Added or updated test cases to test new features

Checklist:

• I have checked to make sure no other pull requests are open for this issue
• The code is properly formatted and is consistent with the existing code style
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings

Screenshots

[DenverCoder1]

Looks good to me, thanks for contributing!