[Flow] - type the pause actions + reducer

[jasonLaster]

We currently type the sources and breakpoints reducers. It would be great to give the same treatment to pausing.

Here's an initial patch. Run this command on a new branch to get started:

curl https://gist.githubusercontent.com/jasonLaster/48a09ff185f13ec7fa0da30298a8603e/raw/b740cc5ee55a698445ba5b19b5fc8cb0c77b1127/foo.diff | git apply

how do i run flow? flow

how do i see a module's coverage? flow coverage --color public/js/utils/source-map-worker.js or npm run flow-coverage

[montogeek]

Colorized diff https://gist.github.com/jasonLaster/48a09ff185f13ec7fa0da30298a8603e