Add Wasm descriptions to in-depth.html, grey out non-default workloads (backmerge of #275)

[danleh]

As discussed in last week's meeting, this is a backmerge of #275 to the 3.0 branch (6588e89):

• Adds descriptions for all Wasm workloads.
• Extends the test to check that the <dt> tag text contents matches the id="..." id property.
• Adds a CSS style for non-default workloads (slightly grayed-out).
• Extends the text to check that all non-default workloads from the JetStreamDriver.js have this CSS class set.
• (very minor drive-by:) Add some padding at the bottom of in-depth.html

Fixes the wasm part of #199

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[danleh]

CC @kmiller68 (Since we already discussed this and it doesn't touch the runner/driver at all, I would merge this as soon as Camillo gives his OK)