feat(translations): add icelandic translations

[egillanton]

Description

I have a pull request here ready to merge the Icelandic language into the project.

• I have read and understand the CONTRIBUTING.md document in this repository

Type of change

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

Checklist:

• Add main translation to packages/translations/src/languages/is.ts
• Update DateFNSKeys to include is
• Add packages/payload/src/exports/i18n/is.ts
• Update packages/payload/src/exports to include is
• Add is translation to all the packages/richtext-lexical/* translation files
• Pass all tests locally - Havn't passed all pnpm run test, but partially, the ones I am not passing have something todo with AWS