temp: adds mako templates and dirs to Studio test env

The content library tests were failing to locate templates when
rendering XBlocks, but since these tests are skipped in CI, the issue
went undetected.

This fix is marked temporary because a proper fix involves adding
lms/templates to the cms.envs.test MAKO_TEMPLATE_DIRS_BASE list. This
was tried, and caused unrelated tests to fail, and so we took this
approach instead. See PR for full details.

cms/envs/test.py

@@ -267,6 +267,12 @@ TEST_ELASTICSEARCH_USE_SSL = os.environ.get(
 TEST_ELASTICSEARCH_HOST = os.environ.get('EDXAPP_TEST_ELASTICSEARCH_HOST', 'edx.devstack.elasticsearch710')
 TEST_ELASTICSEARCH_PORT = int(os.environ.get('EDXAPP_TEST_ELASTICSEARCH_PORT', '9200'))
 
+############################# TEMPLATE CONFIGURATION #############################
+# Adds mako template dirs for content_libraries tests
+MAKO_TEMPLATE_DIRS_BASE.append(
+    COMMON_ROOT / 'lib' / 'capa' / 'capa' / 'templates'
+)
+
 ########################## AUTHOR PERMISSION #######################
 FEATURES['ENABLE_CREATOR_GROUP'] = False