watch files during development both frontend and backend (#336)

.changeset/fair-students-cough.md

@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fix an issue with how files are watched during development

packages/astro/src/runtime.ts

@@ -428,7 +428,7 @@ async function createSnowpack(astroConfig: AstroConfig, options: CreateSnowpackO
       lockfile: null,
     },
     {
-      isWatch: isHmrEnabled,
+      isWatch: mode === 'development',
     }
   );
   const snowpackRuntime = snowpack.getServerRuntime();