feat(cli): add VS Code extension wrapping glint lsp

editors/vscode/ is a TypeScript VS Code extension that starts glint lsp
as a child process and connects to it via vscode-languageclient. The
documentSelector restricts LSP processing to **/.gitlab-ci.yml so other
YAML files are unaffected. The glint.executablePath setting controls the
binary location (default: glint on PATH). Build with task ext-compile;
package as .vsix with task ext-package. Taskfile tasks added:
ext-install, ext-compile, ext-package. Root .gitignore updated to
exclude node_modules/, out/, and *.vsix from the extension directory.

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

.gitignore

@@ -33,6 +33,11 @@ coverage.txt
 *.swo
 *~
 
+# VS Code extension build artifacts
+editors/vscode/node_modules/
+editors/vscode/out/
+editors/vscode/*.vsix
+
 # OS
 .DS_Store
 Thumbs.db