Add .editorconfig for code style consistency

[Rotzbua]

No description provided.

[ByteHamster]

Before reformatting files, I think we should have a CI check that enforces the formatting. Otherwise the files will soon be inconsistent again

[Rotzbua]

Before reformatting files[..]

I removed the commit which formats some files from this PR to avoid conflict with other PRs. Formatting the files can be done by you so it does not require extra review.

I think we should have a CI check that enforces the formatting.

I never used a lint tool for editorconfig. Until now, I considered editorconfig to be an automatic text editor configuration rather than a strict style rule.
But I am open to new useful tools if they exist?