Extract client creation

Also default to use the language server version in the user agent

actions-languageserver/src/client.ts

@@ -0,0 +1,9 @@
+import {Octokit} from "@octokit/rest";
+import {version} from "../package.json";
+
+export function getClient(token: string, userAgent?: string): Octokit {
+  return new Octokit({
+    auth: token,
+    userAgent: userAgent || `GitHub Actions Language Server (${version})`
+  });
+}