Express Release: Docs and site changes

[gadenbuie]

Feature branch to collect all Express-related documentation and website updates.

For posit-dev/py-shiny#969

Dev Notes

• Target any Express-related updates on this branch.
• Please prefer leaving commit history in tact and using merge commits. Alternatively use PR branch for git history revisions.

Previewing

The shinylive examples in the deployment previews use the current PyPi release of packages, but the examples and writing target the new release, so many of them will be broken. If you'd like to locally build the site with the latest versions of packages, do:

# First, make sure you can build shinylive
git clone https://github.com/posit-dev/shinylive
cd shinylive
make submodules
make all

# Link shinylive CLI to freshly built assets
pip install shinylive
shinylive assets link-from-local ./build

# Re-build with latest dev versions
cd packages
cd py-htmltools && git pull && cd ..
cd py-shiny && git pull && cd ..
cd py-shinywidgets && git pull && cd ..
cd py-faicons && git pull && cd ..
cd ..
make clean && make all

# Finally, build py-shiny-site from this branch
git clone https://github.com/posit-dev/py-shiny-site
cd py-shiny-site
git checkout rc-express
make serve

[gshotwell]

This looks great, a few review comments which are optional

[gshotwell]

I don't think this screenshot matches the template so we should change the photo.

[gshotwell]

Suggested change

	This isn't because we think it's better, but because Shiny Express's advantages---being more approachable and more concise---are fairly self-evident, while Shiny Core's advantages are more subtle.
	This isn't because we think it's better overall, but because Shiny Express's advantages---being more approachable and more concise---are fairly self-evident, while Shiny Core's advantages are more subtle.