[L] Change in coreboot[main]: Documentation: Add information about the site-local directory

[Martin L Roth (Code Review)]

Martin L Roth has posted comments on this change by Martin L Roth. ( https://review.coreboot.org/c/coreboot/+/87185?usp=email )

Change subject: Documentation: Add information about the site-local directory
......................................................................

Patch Set 1:

(1 comment)

File Documentation/getting_started/site-local.md:

PS1:
> Looking at the content in `managing_local_additions. […]

I completely agree with what they have. It might be good to go back and rework our documentation at some point. Right now I'm focusing mostly on the `reference` area, which is something that we're sorely lacking.

I've got some more that I plan to push in the upcoming week or so:
- Chip operations
- Device Operations
- Resource Allocator
- coreboot tables
- cbmem_util

And some I plan to do but haven't started yet:
- coreboot toolchain
- Make build targets

Let me know if you have any other thoughts or think we need specific documentation.