Add trailing slash to site_url

`site_url` has to end with a trailing slash, because when MkDocs processes the Jinja2 templates, it will embed a script tag into the final html: ```js <script id="__config" type="application/json">{"base": "/some/path/4.1.1", ...}</script> ``` The JS-relevant part of mike then handles this as follows `fetch(ABS_BASE_URL + "../versions.json")` or, if you look at the actual js-bundle: `new URL("../versions.json", t.base)` And if `t.base` doesn't end with a trailing slash, the last component is completely ignored, which is obviously not what we want.

Author: cubernetes

mike/mkdocs_plugin.py

@@ -46,7 +46,7 @@ def on_config(self, config):
  if version and config.get('site_url'):
  if self.config['canonical_version'] is not None:
  version = self.config['canonical_version']
- config['site_url'] = urljoin(config['site_url'], version)
+ config['site_url'] = urljoin(config['site_url'], version) + '/'
 
  def on_files(self, files, config):
  if not self.config['version_selector']: