docs: esbuild readme

Author: joelgallant

app-config-esbuild/README.md

@@ -0,0 +1,28 @@
+## App Config esbuild
+
+Use app-config with esbuild.
+
+Install:
+
+```sh
+yarn add -D @app-config/esbuild
+```
+
+Then add it to your esbuild configuration:
+
+```javascript
+const { createPlugin: appConfig } = require('@app-config/esbuild');
+
+require('esbuild')
+  .build({
+    bundle: true,
+    entryPoints: ['./src/index.ts'],
+    outfile: './dist/index.js',
+    // this is the line we care about
+    plugins: [appConfig()],
+  })
+  .catch(() => process.exit(1));
+```
+
+This will allow you to import `@app-config/main` from your application, with all
+filesystem and other Node.js code stripped out (when using `bundle`).