merge suggest calls

When existing suggestions exist, and you have a custom `@utility` with a
matching root, then we would override the existing utilities which is
wrong.

This ensures that we merge all the groups such that all utilities are
being suggested to the user.

Author: RobinMalfait

packages/tailwindcss/src/utilities.ts

@@ -124,9 +124,12 @@ export class Utilities {
   }
 
   suggest(name: string, groups: () => SuggestionGroup[]) {
-    // TODO: We are calling this multiple times on purpose but ideally only ever
-    // once per utility root.
-    this.completions.set(name, groups)
+    let existingGroups = this.completions.get(name)
+    if (existingGroups) {
+      this.completions.set(name, () => [...existingGroups?.(), ...groups?.()])
+    } else {
+      this.completions.set(name, groups)
+    }
   }
 
   keys(kind: 'static' | 'functional') {