Add editor, prettier, and ignore dotfiles

.gitignore extended for TypeScript/Node build artifacts on top of the
prompts-repo template. .editorconfig and .prettierrc match the prompts
template (4-space indents, prose-wrap always for markdown).

.gitignore

@@ -0,0 +1,34 @@
+# OS
+.DS_Store
+Thumbs.db
+
+# Editors
+*.swp
+*.swo
+*~
+*.bak
+.idea/
+.vscode/
+*.sublime-*
+
+# Node
+node_modules/
+
+# TypeScript / build artifacts
+dist/
+build/
+*.tsbuildinfo
+coverage/
+.nyc_output/
+
+# Vitest
+.vitest-cache/
+
+# Environment / secrets
+.env
+.env.*
+*.pem
+*.key
+
+# quack runtime data (in case anyone runs the CLI from inside the repo)
+.quack/