[S] Change in coreboot[main]: [POC] Docs/lib/timestamp.md: Use Breathe to generate API documentation

[Nicholas Chin (Code Review)]

Nicholas Chin has posted comments on this change by Nicholas Chin. ( https://review.coreboot.org/c/coreboot/+/87231?usp=email )

Change subject: [POC] Docs/lib/timestamp.md: Use Breathe to generate API documentation
......................................................................

Patch Set 2:

(1 comment)

Patchset:

PS2: 
This does slow down the documentation build significantly. Not only does Doxygen take some time to run, Breathe also takes time to parse the Doxygen XML output when it encounters a page that makes calls to it. I suspect this could be improved by a more targeted Doxygen config though, as I basically just enabled it for all files in `src` other than `src/vendorcode` (similar to the old Doxygen config) just to get something to work.