implements not a keyword in js

Author: sheetalkamat

src/harness/fourslash.ts

@@ -4557,6 +4557,7 @@ namespace FourSlashInterface {
                 switch (keyword.name) {
                     case "enum":
                     case "interface":
+                    case "implements":
                     case "private":
                     case "protected":
                     case "public":

src/services/completions.ts

@@ -1989,6 +1989,7 @@ namespace ts.Completions {
             case SyntaxKind.DeclareKeyword:
             case SyntaxKind.EnumKeyword:
             case SyntaxKind.GlobalKeyword:
+            case SyntaxKind.ImplementsKeyword:
             case SyntaxKind.InferKeyword:
             case SyntaxKind.InterfaceKeyword:
             case SyntaxKind.IsKeyword: