Fix reference to twbs/examples/icons-font + fine-tune index.html SB location target

[julien-deramond]

Description

Some links in https://twbs-bootstrap.netlify.app/docs/5.3/examples/ redirect to the right StackBlitz environment, but not always directly to the index.html which can be in src directory.

This PR shows a way to fix it. It might over-complexify the algorithm.
3 possibilities:

• this PR is OK
• we don't care and keep the current situation not perfect
• we choose to link to / instead of /index.html which will point out to the README.md and it would be valid for each environment.

⚠️ This PR also fixes the link to the "Bootstrap Icons" correct StackBlitz environment. It might be treated in another PR if needed.

/cc @XhmikosR

Type of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist

• I have read the contributing guidelines
• My code follows the code style of the project (using npm run lint)
• My change introduces changes to the documentation
• I have updated the documentation accordingly
• (N/A) I have added tests to cover my changes
• All new and existing tests passed

Live previews

• https://deploy-preview-38310--twbs-bootstrap.netlify.app/docs/5.3/examples/

[XhmikosR]

There's a balance between everything and some things might make more sense to keep them simple :)

Even if the index.html is not found, StackBlitz redirects so it's sort of OK. That being said, I don't mind with the current solution for now, but you need to escape any characters and construct the URL param automatically not manually (/ should be %2F).