Prerelease docs missing HTML

Looks like some omitted code quoting has caused some HTML to be stripped out of the [release notes](https://github.com/chanan/BlazorStrap/releases/tag/v5.2.100-Preview1), rendering them indecipherable.

I was able to recover what I _think_ was intended from the [VNext docs](https://blazorstrap.io/VNext/V5) page. (At least my test code seems to run ok.)

Although also the "in your layout put the `BSCore`" thing is probably at the wrong indent level, since that's not related to `_Imports.razor`. And I'm not sure showing an invalid `integrity` value like that is helpful -- or at least is less helpful than adding a paragraph with a link telling people when and how to get a real value to put there. (And it wouldn't be needed in a typical Blazor app, since it's in wwwroot.)

----
On a side note, I came looking for this update specifically due to some weird threading behaviour of BSModal in older versions (the Shown and Hidden events being called back not on the render thread, and various things returning before actually complete) -- I'm happy to say that the new preview (or actually Preview3, which seems to exist in NuGet but not GitHub Releases?) is behaving a lot more "sensibly" in these regards, though I've yet to test it in a larger app.

Start by comparing the v5.2.100-Preview1 release notes with the linked VNext V5 documentation page. Restore the omitted HTML/code quoting, correct the BSCore indentation, and clarify the integrity guidance so the release notes render understandably and provide valid setup instructions.

Written by the indexing model from the issue text.