Document how to rebuild package fast

[senpl]

Subject

build

Description

Current guidleines instruction not include information how to build cypress fast.
Rebuild whole project takes around 3 minutes. There probably exist faster way to check changes in one package (eg. driver) file.
I currently do
yarn postinstall & yarn start
but there are probably faster feedback loop to check changes.

[MikeMcC399]

@senpl

Are you referring to the https://github.com/cypress-io/cypress/blob/develop/CONTRIBUTING.md guide ? And are you suggesting that some additional information is needed in that document to speed up working with the Cypress source code?

[senpl]

Yes. Just to make contributing easier for this that starts.
What package could be tested without long rebuild process and how programmers check their changes fast.
Also additional info about what build steps do would be nice, to share light into what is really needed and what could be skipped.
Anyway basic code change -> change check guide/instructions would be nice.