docs: noting that Provider includes Portal.Host

[meatnordrink]

Summary

The existing Portal documentation doesn't note that Provider supplies a Portal.Host; you have to click through to the documentation for Portal.Host to find this out. This is key information for using this component, and should be available on this page.

I also corrected a grammatical error in the same paragraph.

Test plan

Load the documentation; the extra sentence should be added.

[lukewalczak]

Hey @meatnordrink, please rename the commit message according to the convention mentioned in doc in order to merge that PR.

[meatnordrink]

Hey @lukewalczak, sorry for the long delay getting back to this - it had fallen off my radar.

Thanks for changing the title to match the conventions! I'm honestly not sure how to change the commit message on this, since I created this commit via the GitHub UI, rather than by actually cloning the repo.

If necessary, I can make a new PR with the correct commit messaging and tag you.

[callstack-bot]

Hey @meatnordrink, thank you for your pull request 🤗. The documentation from this branch can be viewed here.