Add the activate github jinja template

This should allow the activation of a virtual python env on GH

Contributes to CURA-9365

generators/VirtualPythonEnvResources/activate_github_actions_buildenv.jinja

@@ -0,0 +1,2 @@
+{% for var, value in envvars.items() %}echo "{{ var }}={{ value }}" >> $GITHUB_ENV
+{% endfor %}