Add project metadata files

- CHANGELOG.md: Version history (v1.0.0)
- .nvmrc: Node.js version (20)
- .editorconfig: Code style configuration
- CONTRIBUTING.md: Contribution guidelines

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.editorconfig

@@ -0,0 +1,20 @@
+# EditorConfig - https://editorconfig.org
+
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+indent_style = space
+indent_size = 2
+insert_final_newline = true
+trim_trailing_whitespace = true
+
+[*.md]
+trim_trailing_whitespace = false
+
+[*.json]
+indent_size = 2
+
+[Makefile]
+indent_style = tab