Remove support for NodeJS v10.x

[cassels]

NodeJS v10.x is now EOL and supporting it is becoming harder.

• chore: upgrade to yarn3 #198
  Upgrading to use Yarn v3 means that we can no longer develop or test on NodeJS v10.x. See migration notes.
• chore: use actions/setup-node #210
  CI is no longer testing/linting/building on NodeJS v10 because of the above yarn v3 point so we cannot guarantee dotpref works on NodeJS v10.
• chore(deps): update dependency mem to v9 - autoclosed #219
  mem@9.x has dropped support for NodeJS v10 as it is pure ESM.
• chore(deps): update dependency pkg-up to v4 - autoclosed #230
  pkg-up@4.x has dropped support for NodeJS v10 as it is pure ESM.
• chore(deps-dev): update dependency @types/write-file-atomic to v4 #269
  npm/write-file-atomic@4.x has dropped support for NodeJS v10.