Move esbuild configuration to build.mjs.

In preparation for Surfer webview integration.

build.mjs

@@ -0,0 +1,30 @@
+import * as esbuild from 'esbuild';
+
+const mode = (process.argv[2] ?? 'build');
+
+const commonOptions = {
+    logLevel: 'info',
+    bundle: true,
+    target: 'es2021',
+    sourcemap: 'linked',
+    outdir: 'out/',
+};
+
+const extensionContext = await esbuild.context({
+    external: ['vscode'],
+    format: 'cjs',
+    platform: 'node',
+    entryPoints: {
+        'extension': './src/extension.ts',
+    },
+    ...commonOptions
+});
+
+if (mode === 'build') {
+    await extensionContext.rebuild();
+    await extensionContext.dispose();
+} else if (mode === 'watch') {
+    await extensionContext.watch();
+} else {
+    console.error(`Usage: ${process.argv0} [build|watch]`);
+}

package.json

@@ -341,8 +341,8 @@
     "lint": "eslint --fix",
     "tsc": "tsc --project tsconfig.json",
     "tsc:watch": "npm run tsc -- --watch",
-    "esbuild": "esbuild ./src/extension.ts --bundle --sourcemap --outdir=out/ --format=cjs --platform=node --external:vscode",
-    "esbuild:watch": "npm run esbuild -- --watch",
+    "esbuild": "node build.mjs build",
+    "esbuild:watch": "node build.mjs watch",
     "vscode:prepublish": "npm run lint && npm run tsc && npm run esbuild",
     "package": "vsce package"
   },