Add a redirection on index.html to clean url

[sfauvel]

Content

When we access to the documentation with index.html at the end of the url (https://mithril.network/doc/index.html), the page content is displayed twice.

We inject a javascript in the doc/index.html to redirect to the clean url without index.htmlat the end.
The script is added at the beginning of the index.html.

<script type="text/javascript"> 
if (window.location.href.endsWith("/index.html")) {
    end_of_clean_url = window.location.href.lastIndexOf("/");
    window.location.href = window.location.href.substring(0, end_of_clean_url);
}
</script>

Pre-submit checklist

• Branch
  • Tests are provided (if possible)
  • Crates versions are updated (if relevant)
  • CHANGELOG file is updated (if relevant)
  • Commit sequence broadly makes sense
  • Key commits have useful messages
• PR
  • No clippy warnings in the CI
  • Self-reviewed the diff
  • Useful pull request description
  • Reviewer requested
• Documentation
  • Update README file (if relevant)
  • Update documentation website (if relevant)
  • Add dev blog post (if relevant)

Comments

The issue is referenced in docusaurus repository: facebook/docusaurus#10059

Issue(s)

Closes #1867

[github-actions]

Test Results

    4 files  ±0     52 suites  ±0   9m 19s ⏱️ +4s
1 191 tests ±0  1 191 ✅ ±0  0 💤 ±0  0 ❌ ±0 
1 357 runs  ±0  1 357 ✅ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit cd369d0. ± Comparison against base commit 7a7396e.

♻️ This comment has been updated with latest results.

[dlachaume]

Just a minor comment, otherwise LGTM 👍