Allow using new CodeQL languages without updating the CodeQL Action

src/languages.ts

@@ -1,6 +1,10 @@
-// All the languages supported by CodeQL
+/**
+ * A CodeQL language.
+ *
+ * To facilitate adding new languages, this is _not_ an exhaustive list of
+ * languages supported by CodeQL.
+ */
 export enum Language {
-  actions = "actions",
   csharp = "csharp",
   cpp = "cpp",
   go = "go",

src/start-proxy.ts

@@ -11,18 +11,14 @@ export type Credential = {
   token?: string;
 };
 
-const LANGUAGE_TO_REGISTRY_TYPE: Record<Language, string> = {
+const LANGUAGE_TO_REGISTRY_TYPE: Partial<Record<Language, string>> = {
   java: "maven_repository",
   csharp: "nuget_feed",
   javascript: "npm_registry",
   python: "python_index",
   ruby: "rubygems_server",
   rust: "cargo_registry",
   go: "goproxy_server",
-  // We do not have an established proxy type for these languages, thus leaving empty.
-  actions: "",
-  cpp: "",
-  swift: "",
 } as const;
 
 // getCredentials returns registry credentials from action inputs.