tools: add direct anchors for error codes
This adds direct anchors for the error codes in errors.html. For example, previously the anchor for ERR_ASSERTION is #errors_err_assertion, now there is also #ERR_ASSERTION.
Checklist
-
make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
documentation is changed or added -
commit message follows commit guidelines
Affected core subsystem(s)
tools, doc