Pr/example for converting regular reducer to undoable one

[mohinderps]

Please check if the PR fulfills these requirements

• Is this just a doc change? yes

• If no, then check that:

  • The commit message(s) are descriptive of the changes made
  • The PR contains changes that are focused and differs from other PRs
  • Tests for the changes have been added where needed
  • Docs have been added / updated

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

Update docs

This PR adds a doc on how to convert a regular reducer to undoable reducer.

[coveralls]

Coverage remained the same at 97.674% when pulling 73b7725 on mohinderps:pr/example-for-converting-regular-reducer-to-undoable-one into 23ef33e on omnidan:master.

[nmay231]

Awesome! So there are a few points to mention.

• First off, the example looks great! 🌟 No complaints there.
• It needs to have a link in docs/summary.md and docs/main/examples/readme.md. Otherwise, people can't find it.
• For some reason, the package-lock was changed (maybe differing versions of npm?) Because that is an unnecessary change, it should be removed.
  If you have access to the command-line version of git, you can run
  git reset package-lock.json master to reset it to the version in master.
  Or I can deal with it when I merge it, either way works.

Thanks 👍

[mohinderps]

Done @nmay231! Let me know if anything else is required too.

[nmay231]

It's all merged! You can check it out here

And my bad, the command you should've used to reset the package-lock was git checkout master package-lock.json. I just fixed that up before merging.

Thanks for contributing! 🌟