feat: add Angular workspace with demo app and library build

- Restructure into standard Angular library workspace
- Library source in projects/ngx-pretext-table/
- Demo app in src/ using PretextVirtualScrollDirective
- Switch @chenglou/pretext dependency to npm registry (^0.0.4)
- Fix moduleResolution to "bundler" for Angular 17 compatibility

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

.gitignore

@@ -1 +1,21 @@
-node_modules
+# Compiled output
+/dist
+/out-tsc
+
+# Node
+/node_modules
+
+# Angular cache
+/.angular/cache
+
+# IDEs
+.idea/
+.vscode/*
+!.vscode/settings.json
+!.vscode/tasks.json
+!.vscode/launch.json
+!.vscode/extensions.json
+
+# System
+.DS_Store
+Thumbs.db