Add DiKTat specific configuration and GitHub Action

[0x6675636b796f75676974687562]

Description

This change:

• adds the Kotlin style guide compliant .editorconfig;
• enables the DiKTat static analysis plug-in, and
• adds the corresponding GitHub Action (SARIF reports will be available under Security -> Code scanning alerts).

Please see the README in this template reporitory for more details.

Type of Change

• Minor bug fix (non-breaking small changes)

How Has This Been Tested?

Manual Scenario

Run either

• gradlew --continue diktatCheck to see the list of DiKTat warnings in plain text format, or
• gradlew --continue diktatCheck -Pdiktat.githubActions=true to generate DiKTat warnings in the SARIF format.

Checklist (remove irrelevant options):

• The change followed the style guidelines of the UTBot project
• Self-review of the code is passed
• The change contains enough commentaries, particularly in hard-to-understand areas
• No new warnings
• All tests pass locally with my changes

[orchestr7]

We will migrate it to a stable version later. We had some problems with 1.7 kotlin in last release.
Probably we need to disable an action by for now.

Also UTbot team for sure will get tons of warnings, so may be at least by for now we will disable it?

And in the second PR we will run diktat -fix to fix all issues automatically

[orchestr7]

@denis-fokin at least approve workflow :)