Website tweaks

[chrsmith]

Collection of issues post GREAT WEBSITE MIGRATION OF 2019

• We serve a few .webp images for blog posts, but it looks like the image format isn't supported on Safari. Example: see the "Running Containers in AWS..." feature image on https://www.pulumi.com/blog/tag/containers/.

• Author avatar images get stretched in odd ways on mobile. Navigate to https://www.pulumi.com/blog/author/chris-smith/ and make the window super-duper teeny-tiny. We should set a min-size of the image and/or constrain how it shrinks?

• Do we still have the short links for /help/...? We still have some URLs baked into the pulumi/pulumi code that reference things like https://pulumi.io/help/stack-reference. Is there an updated version of that?

• h6 seems to be formatter as ALLCAPS, even when styling an inner code element? (see https://www.pulumi.com/docs/reference/programming-model/#dependson)

  

  These are <h6><code>dependsOn</code></h6>

• The highlighting of currently selected section in the nav is barely noticeable

• We seem to be generating an rss.xml file for all sections; is there a way to make it only generate for /blog/rss.xml? (Only generate an RSS feed for the blog #1420)

[justinvp]

• Do we still have the short links for /help/...?

We should discuss what we want to do with these. See https://github.com/pulumi/pulumi-service/pull/3716#discussion_r300465434

[justinvp]

I checked off the "short links" bullet above per https://github.com/pulumi/pulumi-service/pull/3716#issuecomment-509262571 and #1293

[justinvp]

I also added a couple bullets from #1213 (I'm going to close #1213)