feat(ci): add post pull script to run install

[OnkarRuikar]

People have faced issues after pulling new code from origin or base and they have spent hours figuring out what was wrong. Almost all the time simple yarn install makes thing right again.

The PR adds post-merge script which runs when a contributor runs git pull or git pull upstream main. The script has following properties:

• it works only if the branch is main
• do yarn install on very first run
• when pulled code has package.json modified then run yarn install <-- this is the main feature
• do nothing if package.json hasn't been modified since last pull

Yari does yarn install on every precommit, which will be very annoying in content. Next best thing is to do it immediately after pull/merge in main branch.

[OnkarRuikar]

ping @dipikabh @teoli2003

[dipikabh]

Thanks for adding this feature, @OnkarRuikar. It indeed can be frustrating to realize that all that was needed was a yarn install after trying everything else.

If package.json has changed, what do you think about giving a warning message after pull/merge in main branch, suggesting to run yarn install, rather than doing it automatically?

[OnkarRuikar]

I've updated the feature. Now it gives a warning message instead of actually running the install command.
Also as suggested by @estelle the warning will be shown on every pull till you run the install command. Then till the package.json get's modified there will be no warning on pulls.

[dipikabh]

Thanks for adding the warning message, @OnkarRuikar

[dipikabh]

Hi @OnkarRuikar, feel free to ping one of us to merge this after you've had a chance to fix the failing check. Thanks!