Add EditorConfig file

[AlexWayfer]

More info here: https://editorconfig.org

Also fix issues with newlines and trailing whitespaces.

[Forty-Bot]

I think it is better to just add stuff like this to gitignore and let users configure their editor however they want.

[AlexWayfer]

I think it is better to just add stuff like this to gitignore and let users configure their editor however they want.

No, this stuff exactly for VCS. For single style between all contributors. If somebody will write a code (or documentation or something else) with trailing spaces, then somebody else will have enabled setting for deleting trailing spaces, yet another will indent with tabs, and fourth will use spaces for indentation… it's a mess. And this file, tool, is intended for unifying. If you don't want it and mixing spaces with tabs and unrelated changes of trailing spaces and newlines are OK for you — OK. But I still recommend this.

[Forty-Bot]

It's ok to have a standard style, but I'd rather enforce something like that with one of the many c++ formatters. Plus, no config can support every editor without plugins. It is better to let users add whatever config they need, imo.

[AlexWayfer]

I'd rather enforce something like that with one of the many c++ formatters

OK, I agree with it. But it will not help with Markdown, JSON and other files.

Plus, no config can support every editor without plugins.

Sorry, what? This file is not preventing opening the project in some editor without its support. And it's not hard to setup an editor for automatic support of defined (in this file) rules. Or, if you have an editor without such possibility, of course you can just read this file as guidelines and make it manually. But it'd be an argument for PR reviews.

It is better to let users add whatever config they need, imo.

One more time: if one user adds their config with tabs indentation, and another user adds with spaces indentation — it's OK as freedom but it's bad as single-project-style. You can ignore this file, but for users with EditorConfig support and for reviewers it'd be easier to write correct (suitable) code.