Typescript config parity with Browsertrix repo (#289)

Follow-up from #288 

This matches the strictness rules with the Browsertrix repo,
specifically `noImplicitAny`, and then adds `// @ts-expect-error`s to
suppress existing errors this change raises. This'll help us keep code
quality high moving forward.

Going to just directly merge this once it passes CI; as with #288, this
doesn't change any code, just comments.

src/embed-receipt.ts

@@ -357,6 +357,7 @@ export class RWPEmbedReceipt extends LitElement {
     `;
   }
 
+  // @ts-expect-error [// TODO: Fix this the next time the file is edited.] - TS7006 - Parameter 'event' implicitly has an 'any' type.
   onEmbedDrop(event) {
     event.stopPropagation();
     this.active = !this.active;