Update GitHub Actions workflow to clone specific branch and change custom_template_dir type to string

Author: JakubAndrysek

.github/workflows/mkdoxy-test-demos.yaml

@@ -24,7 +24,7 @@ jobs:
           python -m pip install -e ".[dev]"
           sudo apt-get install doxygen
       - name: Clone test repo
-        run: git clone https://github.com/JakubAndrysek/MkDoxy-demo.git demo
+        run: git clone --branch core-update https://github.com/JakubAndrysek/MkDoxy-demo.git demo
       - name: Build docs
         run: |
           cd demo

mkdoxy/doxy_config.py

@@ -47,7 +47,7 @@ class MkDoxyConfigProject(Config):
     doxy_config_default = c.Type(bool, default=True)
     doxy_config_file = c.Optional(c.Type(Path))
     doxy_config_file_force = c.Type(bool, default=False)
-    custom_template_dir = c.Optional(c.Type(Path))
+    custom_template_dir = c.Optional(c.Type(str))
 
 
 class MkDoxyConfig(Config):