chore: Add & apply yarn deduplicate

[Bnaya]

Motivation:
yarn is actually missing automatic dedup of deps,
Which leads to multiple-but-compatible versions of deps.
yarn-deduplicate is a complementary tool to solve that.

It's recommended to run it after any dependencies add/remove/upgrade

Related:
yarnpkg/yarn#3778
(And there are more issues around yarn repo related to that)

[coveralls]

Coverage remained the same at 93.275% when pulling 52ef3b3 on apply-yarn-deduplicate into a3ec6b1 on master.

[mweststrate]

Thanks! Interesting tool, not sure we really needed, but if it works without prob, might make it slightly faster for people to contribute

[Bnaya]

The yarn.lock got little bit smaller,
means the node_modules was little bit bigger and nested than it could be.
in some repos deduping cleaning up maybe third of the lock file.

[danielkcz]

Wouldn't it be better to just npx yarn-deduplicate? Adding it to deps it's not exactly sure what it has done because some other deps got in there.