Initial URL for BlazorWebView

[guardrex]

Fixes #28965

cc: @mkArtakMSFT ... I can see that Surayya did the PR ... I'll ping for review.

Notes:

• Do we want to use this language to describe the default start path? ...

  The default start path is the relative root URL path (/).

  ... because I'm not aware if it's possible for these apps to have a different base path. I'll modify to your best choice of language there.

• Just FYI ... Across the Hybrid docs, we use the approach for setting properties on a BlazorWebView that the tutorials adopt. In the case where the dev is looking at the XAML markup code, we show the setting on the element, not via the designer property tools. In the WinForms case, we set those properties in C#, so that's what we place here. We assume the reader used our tutorials, so we assume they'll work with the properties across the docs the same way as the tutorials have them work with them. Just letting you know. This is subject to change later perhaps, but this is the approach we're using thus far.

[surayya-MS]

Looks good to me!

[surayya-MS]

Do we want to use this language to describe the default start path? ...
The default start path is the relative root URL path (/).
... because I'm not aware if it's possible for these apps to have a different base path. I'll modify to your best choice of language there.

This language looks good to me. @Eilon , what do you think?

[danroth27]

LGTM

[guardrex]

Shall we wait on @Eilon to look at that phrasing before merging?

[Eilon]

Yeah I think this is fine, thanks for checking. If for some reason we ever see in the future that it is unclear to someone, we can revisit, but I'd be surprised.