Tsify rison.js (#4510)

* Tsify rison.js

* Turn eslint back on

* Improve typing, cleanup code

* Matt comments

* Prettier-ignore a type declaration

* A couple small type tweaks

lib/common-utils.ts

@@ -0,0 +1,34 @@
+// Copyright (c) 2022, Compiler Explorer Authors
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+//     * Redistributions of source code must retain the above copyright notice,
+//       this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above copyright
+//       notice, this list of conditions and the following disclaimer in the
+//       documentation and/or other materials provided with the distribution.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+
+export function isString(x: any): x is string {
+    return typeof x === 'string' || x instanceof String;
+}
+
+// Object.keys is typed as returning :string[] for some reason
+// This util is for cases where the key is a union of a few possible keys and we
+// want the resulting array properly typed.
+export function keys<K extends string | number | symbol>(o: Record<K, any>): K[] {
+    return Object.keys(o) as K[];
+}