pre-commit: setup prettier to autoformat relevant YAML files

[consideRatio]

This resolves #805 by:

• Adding a .pre-commit-config.yaml file to run prettier specifically
• Adding a .prettierignore file to ignore
  • Helm templates
  • SOPS encrypted content
  • Markdown and JSON, but not YAML files
• Running prettier on all YAML files
• Setting up 2i2c-org on github to use pre-commit.ci for this repo

Review

• The .pre-commit-config.yaml file
• The .prettierignore file
• All autoformatted .yaml files (I saw no issues)

[choldgraf]

This seems reasonable to me - I like the idea of standardizing what we can, especially things as finnicky as YAML

[consideRatio]

With two approvals, and a perception that it's up to me to hit merge, I went for it now that I had some time and ability to context switch to this.