Enable various eslint rules (#1773)

## Description:

Enable various eslint rules.

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

src/client/FlagInputModal.ts

@@ -9,7 +9,7 @@ export class FlagInputModal extends LitElement {
     close: () => void;
   };
 
-  @state() private search: string = "";
+  @state() private search = "";
 
   createRenderRoot() {
     return this;