fix: disable postinstall script prior to publishing

[brandonlenz]

Note!!:

The alternative to this is to roll back husky to v4: #926. We should merge one and close the other + delete the branch.

Due to Husky v5 currently causing more headaches than it may be worth, I recommend rolling back to v4 (PR linked above)

Summary

Husky 5's implementation is a bit different and required adding a postinstall script to package.json. This script should only be ran while developing, not for users of the packaged artifact.

Solution is to disable post install scripts before publishing. This is what pinst was added for in #867, however I missed adding the disable. (See pinst usage for more info)

closes: #923

How To Test

1. Checkout this branch:

git fetch
git checkout bl-fix-husky-packaged-post-install-923

2. Perform a clean install to verify dev still works (I deleted node_modules and ran yarn to verify, plus the ability to commit this and see the git hooks still working with husky were good tests)

3. Locally running yarn prepublishOnly should run the existing test and linting scripts as well as disabling postInstall:
   
   

4. locally running yarn postpublish should result in postInstall being enabled once again:
   
   

5. Finally, testing an install of this package after release of this code change will be the true test.

[brandonlenz]

In the original PR I added a newline to this .gitignore because it's generally good practice for files to end with newlines. However, every time husky install runs (which happens after every yarn install, it updates this file. Might as well merge it in this PR so it won't show up as a random diff for anyone.

[brandonlenz]

For reference since github doesn't really show this change very well on the Conversation tab:

[trussworks-infra-zz]

	Warnings
⚠️	Changes were made to package.json, but not to yarn.lock - Perhaps you need to run yarn install?

Generated by 🚫 dangerJS against 09aa811

[brandonlenz]

Closing as we are going with #926 for the near-term at least.