add rollup bundler for vscode extension

editors/code/rollup.config.js

@@ -0,0 +1,27 @@
+import typescript from 'rollup-plugin-typescript';
+import resolve from 'rollup-plugin-node-resolve';
+import commonjs from 'rollup-plugin-commonjs';
+import nodeBuiltins from 'builtin-modules';
+
+export default {
+    input: './src/extension.ts',
+    plugins: [
+        typescript(),
+        resolve(),
+        commonjs({
+            namedExports: {
+                // squelch missing import warnings
+                'vscode-languageclient': [ 'CreateFile', 'RenameFile' ]
+            }
+        }),
+    ],
+    // keep these as require() calls, bundle the rest
+    external: [
+        ...nodeBuiltins,
+        'vscode',
+    ],
+    output: {
+        file: './bundle/extension.js',
+        format: 'cjs',
+    }
+};