refactor: default to noImplicitOverride

[GeekyEggo]

Overriding methods in TypeScript is easy... too easy. This pull request adds the override keyword, and defaults to noImplicitOverride. This protects us from future changes that might go unnoticed, for example:

Before - no override keyword, and noImplicitOverride set to false.

1. A future change in @elgato/streamdeck renames onWillDisappear to onDisappear.
2. The plugin builds.
3. The plugin doesn't receive the onDisappear event as the method is overriding onWillDisappear.
4. The plugin breaks quietly.

After - override keyword and noImplicitOverride set to true.

1. A future change in @elgato/streamdeck renames onWillDisappear to onDisappear.
2. The plugin build fails.
3. The Maker updates onWillDisappear to be onDisappear as part of the upgrade, and everything works.