Add typing information to get/set proxy typing

[smwhr]

Checklist

• [x] The new code additions passed the tests (npm test).
• [x] The linter ran and found no issues (npm run-script lint).

Description

https://discord.com/channels/329929050866843648/803691019039277128/1000342424880697355

Improved typing informations on proxy and get/setter