[SEO] Remove .html from generated in breadcrumbs and DocFX API navigation tree

[pepinho24]

Describe the bug
Links generated in breadcrumbs and DocFX API navigation tree end with .html

To Reproduce
Example: https://docs.telerik.com/blazor-ui/components/map/overview
The light green are redirects: in the breadcrumb

Example: https://docs.telerik.com/devtools/wpf/api/telerik.windows.controls.raddocking - in the side tree and also internal

Expected behavior
For SEO optimizations, the generated URLs should not end with .html

Additional context

[pepinho24]

1. The breadcrumb issue could be fixed in the following line, where the url property should have the .html stripped:
   https://github.com/telerik/docs-seed/blob/master/_plugins/navigation.rb#L214
   "<a href='#{baseurl}#{url.gsub(".html", "")}'>#{format_title(title)}</a>#{so_far}"

2. The API pages are generated by DocFX where we have little to no control. Ultimately, we might need to create a solution similar to the one stripping out the .html extension in the sitemap, discussed in API ref generated by DocFX adds .html extension to links in sitemap.xml #250

[jivanova]

@nikolay-nenkov @Mike4o

Could you please plan this with priority as it is related to the SEO of the docs site?

// side effect from #250