AG-11598 - Add prettier

[taktran]

Allow prettier to run on all the files (ignoring most of the repo that has not been formatted yet)

nx format:check --all
# Runs without error

Or for specific projects

nx format:check --projects [projects]

# eg,
nx format:check --projects ag-grid-docs

To auto fix prettier issues (may need to remove from .prettierignore if the file/folder is in there)

nx format:write --all
nx format:write --projects ag-grid-docs

Also formats on save in VS Code (respecting the .pretterignore file)

Changes

• Format ag-grid-docs + some root files
• Add .prettierignore file to ignore most of the repo, so prettier can run on the root level
• Move .prettierrc from ag-grid-docs to the root level
• Add .git-blame-ignore-revs to ignore prettier fixes in git blame - see how to exclude commits in blame
• Add format on save for VS Code (does not apply to folders in .prettierignore)

Future work

• Prettier-fy all files - can remove from .prettierignore as we go