use per-method packages instead of a single import for lodash

[mprast]

Changes Made

Changed the lodash import to only import methods that are actually used, so we don't have to download & install the whole package. This is the first of the three changes suggested in #383.

One important thing worth mentioning is that lodash appears to be pulling support for single-method packages going forward. As laid out in the linked article, the official response from lodash to those not wishing to import the full 1.4MB package is now "let the bundler handle it", which suggests to me that either the server-side case was not considered, or the server-side case was considered and judged not to be a priority. I leave it up to you all whether staying on lodash 4 is worth the space savings or not

Also, FYI - your contributing guide appears to be out of date.

Potential Risks

Only risk is typoes, or breaking api changes between the all-in-one lodash package and the per-method packages.

Test Plan

no new functionality added - just need to run CI and do any necessary manual testing to ensure there aren't regressions.

Checklist

• I've increased test coverage
• [x ] Since this is a public repository, I've checked I'm not publishing private data in the code, commit comments, or this PR.