Makefile: make Pelican fail on error

Definitely a sane default to not return non-zero on error... 🤦

Makefile

 PELICAN=pelican
-PELICANOPTS=
+PELICANOPTS=--fatal errors
 
 DEFAULT_LANG=$(shell python -c "`grep "^DEFAULT_LANG" pelicanconf.py`; print(DEFAULT_LANG)")
 SITEURL=$(shell python -c "`grep "^SITEURL" pelicanconf.py`; print(SITEURL.replace('/', '\/'))")