chore: project setup and tooling cleanup (#26)

* add project setup

* add tools to eslint

* remove contributing.md

* update claude md

* chore: simplify CI to single Node.js version (22)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* use node 20

* adjust formatting

* fix linting

* format

* fix layout

* fix: align CI node version to .nvmrc (22), remove redundant gotcha

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: arkon <arkon.85@hotmail.com>

.editorconfig

@@ -0,0 +1,12 @@
+root = true
+
+[*]
+indent_style = space
+indent_size = 2
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[*.md]
+trim_trailing_whitespace = false