Replace pika with microbundle

[jnicklas]

Pika doesn't play well with the monorepo architecture that we have. Because it has its own package.json file in pkg, the main effection package is essentially unusable from other packages in the repo. With microbundle we don't have this problem.

[github-actions]

A preview package of this pull request has been published with the tag microbundle.
You can try it out by running the following command:

$ npm install effection@microbundle

or by updating your package.json to:

{
  "effection": "microbundle"
}

Generated by 🚫 dangerJS against 6b80aaa

[cowboyd]

I ran this against the bigtest test suite which was all green