Summary:
The `BUCK` build files' indentation are 4 spaces large. This PR adds a small modification to `.editorconfig` to reflect that. Especially important for them, because an improperly indented line would be a syntax error.
Pull Request resolved: https://github.com/facebook/react-native/pull/21554

Differential Revision: D10247954

Pulled By: TheSavior

fbshipit-source-id: 98596a563e9f8c36060cd8aa702757eff230c4c3

Summary:
In most .gradle files, lines are indented with 4 spaces, but in some places they are indented with 2 spaces. This PR fixes them and enforce it by adding .editorconfig settings.
Closes https://github.com/facebook/react-native/pull/10267

Differential Revision: D4048335

Pulled By: lacker

fbshipit-source-id: df2f2556380f56672cf85690eb1c80e640a6aedf