fix: use esbuild inject api to ensure exec order & polyfill (#104)

Author: jthegedus

src/files/handler.js

@@ -1,5 +1,3 @@
-import '@sveltejs/kit/install-fetch'; // eslint-disable-line import/no-unassigned-import
-
 // TODO: hardcoding the relative location makes this brittle
 import {init, render} from '../output/server/app.js';
 

src/files/shims.js

@@ -0,0 +1 @@
+export {fetch, Response, Request, Headers} from '@sveltejs/kit/install-fetch';

src/index.js

@@ -158,14 +158,16 @@ async function prepareEntrypoint({utils, serverOutputDir}) {
 	utils.rimraf(temporaryDir);
 	utils.rimraf(serverOutputDir);
 
-	const handlerSource = path.join(fileURLToPath(new URL('./files', import.meta.url)), 'handler.js');
+	const files = fileURLToPath(new URL('./files', import.meta.url));
+	const handlerSource = path.join(files, 'handler.js');
 	const handlerDest = path.join(temporaryDir, 'handler.js');
 	utils.copy(handlerSource, handlerDest);
 
 	await esbuild.build({
 		entryPoints: [path.join(temporaryDir, 'handler.js')],
 		outfile: path.join(serverOutputDir, 'index.js'),
 		bundle: true,
+		inject: [path.join(files, 'shims.js')],
 		platform: 'node',
 		target: ['node12']
 	});