ci: Add multi-arch docker build support

[Dinip]

Self-hosted support

• Your feature is implemented for the selfhosted version of Swetrix
• This PR only updates the production code (e.g. paddle webhooks, CAPTCHA, blog, etc.)

Database migrations

• Clickhouse / MySQL migrations added for this PR
• No table schemas changed in this PR

Documentation

• You have updated the documentation according to your PR
• This PR did not change any publicly documented endpoints

Description

• Adds support for multi architecture docker builds in amd64 and arm64
• Related with: ci: Add multi-arch docker build support swetrix-fe#428 and Update self-host prerequisites docs#21

Just did a test build run, available here on my docker hub and seems like the multi-arch worked. Also tested on my arm machine and it works as it should.

Note: not sure if you have a specific reason to have the actions version pinned or not, but if you want them pinned to the hash, let me know and I'll revert those changes.

[Blaumaus]

Wow @Dinip, thank you so much for adding this! No reason to have the versions pinned to a commit hash for actions, so what you did looks perfectly fine!

Thanks a lot for contributing!