[core] Use hard tabs in the source for accessibility

[mbrookes]

• I have searched the issues of this repository and believe that this is not a duplicate.

Summary 💡

Hard tabs allow contributors to choose how many spaces a tab represents, which aids accessibility.

Discussion:
rome/tools#425

Examples 🌈

https://github.com/romefrontend/rome

Motivation 🔦

Material-UI as a user interface component library has a strong accessibility ethic. This should extend to contributor DX.

[oliviertassinari]

• Following the default prettier configuration makes it more likely for developers to be able to read our source in GitHub.
• GitHub displays tabs with 4 spaces by default in the UI with no easy way to configure it (there are no global settings in your account, as far as I know). IMHO, it's a deal-breaker if we can't fix it.

[mbrookes]

https://twitter.com/editorconfig/status/610836234676535296

[eps1lon]

Disclosure: I started using tabs in new projects about 6 months ago.

Looking back I always justified spaces with their superiority for manual formatting across environments. Using tabs just didn't work if you wanted to align your SQL queries or hardcoded data structures. But when prettier came along and I grew used to it I never re-evaluated my choice. Since we don't manually format code anymore, tabs are objectively better for a11y and most tools I'm aware of support custom tab-width I don't see a reason to use spaces anymore.

[oliviertassinari]

https://twitter.com/editorconfig/status/610836234676535296

@mbrookes If we can have a default shared configuration of two spaces for tabs, have it work in GitHub and popular text editors, this would work from my end.

[mbrookes]

It all seems to work – I had to adjust my editor to display tabs as two spaces, but that's kind of the point! :)

git diff output is 4 spaces because it outputs tabs, and 4 is the console / pager default, but there's a git config setting for that too.

[oliviertassinari]

Summary of the exploration of #22305. We are waiting for GitHub to come through to resume the changes. We need:

• GitHub mobile support of .editorconfig: [core] Update config to use tab indents #22305 (comment)
• GitHub comments support of .editorconfig: [core] Update config to use tab indents #22305 (comment)