Improve documentation for Performance Hooks entry types

[mmarchini]

Is your feature request related to a problem? Please describe.
Performance Hooks entry types gc, http and http2 are only listed in the docs, there's no explanation about when those are triggered or examples how to use them efficiently.

Describe the solution you'd like
Better documentation for those entry types.

Describe alternatives you've considered
Blog posts? But these can easily get outdated (for example, clearGC mentioned here doesn't seem to be on the API anymore).

[dev-script]

I would like to work on this issue.

[SowmyaGrama]

@dev-script : Have you started work on this? Do you need another helping hand? I am attempting for first time contribution.

[dev-script]

@SowmyaGrama : Not yet but It would be nice if you help. Thanks

[jasnell]

#37136 greatly expands the documentation for these types.