Easier linking between force/reaction

[zephraph]

For more context on this PR, see artsy/reaction#2758. These two PRs should be merged together.

Essentially this adds a mechanism that when in reaction the user can run yarn integrate force to automatically link and start both force and reaction. At the time of this PR, there's no support for starting the linking process while in force.

If you need to do work in force, you'll have to go to react first to run the command. Adding a command in force will be a follow up.

The linking process leaves the package.json/yarn.lock file of force in a dirty state because it actually updates the reference of the linked package (like reaction) to point to a local reference. Running yarn unlink-all will clean up those references. There's a pre-commit hook that will fail if the user tries to commit package.json or yarn.lock in a bad state and give the command to clean it up.

This PR adds a few things:

1. A script called quicklink which controls the linking behavior of a package being linked to force. It is designed to cover reaction but likely will seamlessly handle palette as well.
2. A lint-staged hook on package.json and yarn.lock that fails a commit if linking is still active. The process of linking actually makes a change to the package.json and yarn.lock to point the package to the published package directory.
3. A yarn unlink-all command to easily clean up linking

Through the whole process the tool (yalc) that handles this new linking is kind of abstracted away from the user. I don't yet have a yarn command to directly link a package like reaction from inside force. If that becomes a need we can add it later.

[codecov]

Codecov Report

Merging #4475 into master will increase coverage by <.1%.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           master   #4475     +/-   ##
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+ Coverage    79.3%   79.3%   +<.1%     
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  Files        1269    1269             
  Lines       35404   35493     +89     
  Branches     2059    2063      +4     
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+ Hits        28097   28178     +81     
- Misses       6262    6277     +15     
+ Partials     1045    1038      -7

[damassi]

@zephraph - can you update the main description with the full flow (for the everyday user) of how this works with reaction? I'm not following exactly, assuming i'm working from force. Also not following what needs to be done re linking / unlinking, or why, etc.

[zephraph]

@damassi updated. Does that answer your questions?

[damassi]

Yup, thank you 👍