Fix loading style (#1073)

The style in index.html was getting ripped off on the instance level. I
am not sure why this does not happen on ui level 🤔 But opening the fix
since the current state is a blocker.

Please look at this pr:
NASA-IMPACT/veda-config#424 to see how it looks
like on the instance level.

app/index.html

@@ -59,7 +59,7 @@
       visibility: hidden;
     }
 
-    .loading {
+    .welcome-banner-loading {
       margin-top: 2rem;
       opacity: 0.64;
     }
@@ -114,7 +114,7 @@
         -->
       <h1>{{appTitle}}</h1>
       <p>{{appDescription}}</p>
-      <p class='loading'>Loading...</p>
+      <p class='welcome-banner-loading'>Loading...</p>
     </div>
   </div>
 

postcss.config.js

@@ -1,9 +1,26 @@
+const path = require('path');
+const fs = require('fs-extra');
+const CWD = process.cwd();
+
+const vedaPath = path.resolve(CWD, '.veda/ui');
+const isVedaInstance = fs.existsSync(vedaPath);
+
+let uswdsPath = path.resolve(CWD, 'node_modules/@trussworks/react-uswds/lib');
+
+if (isVedaInstance)
+  uswdsPath = path.resolve(
+    CWD,
+    '.veda/ui',
+    'node_modules/@trussworks/react-uswds/lib'
+  );
+
+const contentPaths = isVedaInstance
+  ? ['.veda/ui/app/**/*.{js,jsx,ts,tsx}', `${uswdsPath}/index.css`]
+  : ['./app/**/*.{js,jsx,ts,tsx}', `${uswdsPath}/index.css`];
+
 let plugins = [require('autoprefixer'), require('postcss-import')];
 const purge = require('@fullhuman/postcss-purgecss')({
-  content: [
-    './app/**/*.{js,jsx,ts,tsx}',
-    '@trussworks/react-uswds/lib/index.css'
-  ],
+  content: contentPaths,
   safelist: {
     deep: [/usa-banner$/],
     greedy: [/^usa-banner/]