Dependabot PR's dont run `postinstall` script

[simondotm]

Dependabot auto versions update is cool, but it doesn't run postinstall script, which generates the package versions manifest for the plugin to use.

Will need to add another action to do this:

on:
  push:
    branches:
      - dependabot/npm_and_yarn/**
  pull_request:
    branches:
      - dependabot/npm_and_yarn/**

... do `pnpm install` and `commit` here