ref-manual: Added two new tips

ref-manual: Added two new tips

Fixes [YOCTO #10297]

Updated the "Other Tips" section to include a couple new tips.

 * Remove the /tmp directory as a way to work-around temporary
   build issues.

 * Create a little method to help you search the massive
   amounts of bits for whatever.  Also, suggested filing bugs
   against the docs if a feature is too hard to find or figure out.

(From yocto-docs rev: d9829dd096f7cc56f8e55fba3190be2a59b80fe5)

Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>