Add custom template example with assets

docs/personal_template/example.md

+{% set curr_repo=subs("mkdocs_template") %}
+# Example
+
+This current documentation you are reading is actually using the custom template
+[Mkdocs Template R.Deville][mkdocs_template_rdeville].
+
+This custom template add a lots of things such as :
+
+  - `.gitlab-ci.yaml` with basic CI file at the root of the repo to later be
+    extended and another CI file to only test and build the documentation,
+  - Workflow files definining some syntax rules such as `.editorconfig`,
+    `.yamllint`, `pyproject.toml` (which also define basic test using `tox`),
+  - `README.md`, a template of README which is automatically updated with the
+    script `post_setup.sh`,
+  - `mkdocs.yml` with more plugins and more configuration than the basic file.
+  - A default `docs/_data/vars.yaml` file,
+  - A complete theme using new plugins defined in `mkdocs.yml` with custom CSS,
+    javascript, images, etc.,
+  - A predefined basic `docs` content,
+  - And many more things.
+
+Below is an example of the rendering of the preview of the basic template and
+the custom template.
+
+
+=== "Basic Template"
+
+    ![!Basic Template Preview][basic_template_preview]
+
+
+=== "Custom Template"
+
+    ![!Custom Template Preview][custom_template_preview]
+
+[mkdocs_template_rdeville]: {{ git_platform.url }}{{ curr_repo.git_slug_with_namespace }}_rdeville
+[basic_template_preview]: /assets/img/basic_template_preview.png
+[custom_template_preview]: /assets/img/custom_template_preview.png
+