add source map support

Summary: Use inline source maps for plugins and main bundle, both in production and development.

Reviewed By: passy

Differential Revision: D9967235

fbshipit-source-id: 245e65c6fea94b93dc34a65ae572b7fc98ad56e1

static/compilePlugins.js

@@ -173,6 +173,9 @@ async function compilePlugin(
           out,
           dev: false,
           sourceMap: true,
+          // due to a bug in metro inline source maps are only created when
+          // sourceMapUrl is truthy: https://github.com/facebook/metro/pull/260
+          sourceMapUrl: 'inline',
         },
       );
     } catch (e) {