chore: add .editorconfig file

[SethFalco]

Topic and Scope

When contributing to the Cookbook app, everyone has different editor settings might may conflict with the project's conventions.

For example, I use spaces over tabs so when I hit the tab key, it inserts necessary number of spaces instead.

This just copies over the .editorconfig from nextcloud/server so that contributors have a more seamless experience when working with the project. As the file defines that the project uses tabs, editors will know to leave tabs as-is.

I removed redundant rules, like *.feature and build/psalm-baseline.xml which aren't relevant to this repository.

Concerns/issues

N/A

Formal requirements

There are some formal requirements that should be satisfied. Please mark those by checking the corresponding box.

• I did check that the app can still be opened and does not throw any browser logs
• I created tests for newly added PHP code (check this if no PHP changes were made)
• I updated the OpenAPI specs and added an entry to the API changelog (check if API was not modified)
• I notified the matrix channel if I introduced an API change

[github-actions]

Test Results

     27 files  1 233 suites   7m 12s ⏱️
   498 tests    498 ✔️ 0 💤 0 ❌
4 482 runs  4 481 ✔️ 1 💤 0 ❌

Results for commit 02914c4.