Create locales for Gahuza and Tigrinya

[DenisHdz]

Resolves #2180

Overall change:
Add moment locales for Gahuza (rw) and Tigrinya (ti).

Code changes:

• Add locale files with months and relative time
• Add unit tests.

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• I have assigned myself to this PR and the corresponding issues
• Automated jest tests added (for new features) or updated (for existing features)
• This PR requires manual testing

[ghost]

Include the correct locale for Gahuza in storybook

[ghost]

Could you check why Jenkins is failing.

[AlistairGempf]

Is there a reason for the Tigrinya locale being named yi rather than ti as it is in the spreadsheet and in the language data?

[DenisHdz]

Is there a reason for the Tigrinya locale being named yi rather than ti as it is in the spreadsheet and in the language data?

You are right, I have created it based on what the issue says. In the moment-ws repo we have ti.
@sadick254 Was it a typo? 😁

[AlistairGempf]

I did a cmd-f for yi and found nothing so I think we're all good ;)

[staylos92]

LGTM 👍