Fix warning in docs and enable strict build mode

add work around for crs<->geom dependency.
enable warnings are errors mode for doc building.

docs/Makefile

@@ -3,7 +3,7 @@
 
 # You can set these variables from the command line, and also
 # from the environment for the first two.
-SPHINXOPTS    ?=
+SPHINXOPTS    ?= -W
 SPHINXBUILD   ?= sphinx-build
 SOURCEDIR     = .
 BUILDDIR      = _build

docs/conf.py

@@ -16,6 +16,16 @@
 sys.path.insert(0, os.path.abspath(".."))
 import odc.geo
 
+# Work-around for type annotation failing due to guarded imports.
+# Some methods in crs return geom types, but geom depends on crs
+# so geom import into crs is only done during typechecking.
+# by patching it here we enable typehinting to find correct types
+# for crs methods that return geometries.
+import odc.geo.crs
+import odc.geo.geom
+
+odc.geo.crs.geom = odc.geo.geom
+
 # -- Project information -----------------------------------------------------
 
 project = "odc-geo"