Improve source file detection and tests

- Use SwiftPM-provided sourceFiles for filtering - Add Utils.swift with
URL descendant check - Update example to use Views/ instead of Folder/ -
Add test for non-included Swift file - Update .zed settings to disable
VSCode CSS language server

Sources/SwiftTailwindExample/NotIncluded.swift

@@ -0,0 +1,5 @@
+// This file is not included in Tailwind.css, so TW classes here will not be generated.
+let html =
+  """
+  <a href="swift.org" class="text-sm">Swift</a>
+  """

Sources/SwiftTailwindExample/Tailwind.css

@@ -4,5 +4,5 @@
 /** You must specify `source(none)` after `tailwindcss` import and add `@source` for each source file / folder you want to include. */
 @import "tailwindcss" source(none);
 @source "./Example.swift";
-@source "./Folder";
-@source "./Folder/**/*.swift";
+@source "./Views";
+@source "./Views/**/*.swift";