chore: enhance development environment

- Add .editorconfig for unified editor settings
- Add .nvmrc to specify Node.js version (20)
- Add useful npm scripts: format, format:check, lint, lint:fix, type-check

.editorconfig

@@ -0,0 +1,20 @@
+# EditorConfig is awesome: https://EditorConfig.org
+
+# top-most EditorConfig file
+root = true
+
+# Unix-style newlines with a newline ending every file
+[*]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+
+# Matches multiple files with brace expansion notation
+[*.{js,jsx,ts,tsx,json,css,scss,md,yml,yaml}]
+indent_style = space
+indent_size = 2
+
+# Markdown files
+[*.md]
+trim_trailing_whitespace = false