Feat: Create `add` cmd script to apply Webpack config changes

### Which areas does this feature request relate to

- [x] Create Plugin
- [ ] Sign Plugin
- [ ] Plugin E2E
- [ ] Plugin Meta Extractor
- [ ] Documentation

### Problem

https://github.com/grafana/plugin-tools/commit/0d4c0399cba9323b513057a6e02b448fea5278ad + https://github.com/grafana/plugin-tools/commit/53784ec5b8d38c25d744d0e6359b233165452a1e were landed as improvements to the experience when scaffolding a new plugin w/ Webpack, but due to the switch to migrations for `update` instead of re-creating all the files, existing plugins cannot benefit from these changes.

### Solution

Create an addition script that allows plugin devs to optionally apply these recent changes.

### Alternatives

_No response_

### Additional context

_No response_

### Are you interested in contributing the solution?

- [ ] Yes
- [ ] No