Add translation support to `va-button`

[jamigibbs]

Description

We have received Spanish translations for "Continue" and "Back" strings which are used in va-button for va-button-pair. We should add i18n support to that component so that they can be translated with the following values:

Spanish

• continue = Continuar
• back = Atrás

Tagalog

• continue = Magpatuloy
• back = Bumalik

Slack convo for reference: https://dsva.slack.com/archives/C01DBGX4P45/p1713890235904039

Details

The translation files are located here in the component-library:

https://github.com/department-of-veterans-affairs/component-library/tree/main/packages/core/src/i18n/translations

You can look at other components that have translation support already as a reference for how to add it to va-button too.

Tasks

• [ ] Add i18next to va-button.
• [ ] Add the provided translations to the translation file(s)
• [ ] Add a va-button-pair Storybook story that demonstrates the translation support

Acceptance Criteria

• [ ] va-button supports the provided translations
• [ ] Storybook has been updated to demonstrate

[caw310]

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[loripusey]

@jamigibbs Here are the Tagalog translations for "Continue" and "Back":

• "continue": "Magpatuloy",
• "back": "Bumalik",