Add a "markup html attribute" example in the documentation that uses a concatenated expression

[BawdyInkSlinger]

Is your feature request related to a problem? When using markup HTML attributes, I occasionally want to use simple expressions as the attribute value (e.g., _id + '-suffix'), but I can never remember the syntax to do that.

Normally I...

1. Try to use a simple expression, incorrectly wrapping it in back-ticks
2. It doesn't work™
3. I try a few other ideas to no avail

4. I give up, settling for:

   <<set _id_attribute = _id + '-suffix'>>
   <span @id="_id_attribute">…</span>

Describe the solution you'd like. These are the current examples:

<span sc-eval:id="_id">…</span>
<span @id="_id">…</span>

I would like the documentation to include two more examples:

<span sc-eval:id="_id + '-suffix'">…</span>
<span @id="_id + + '-suffix'">…</span>

Describe alternatives you've considered. These would be the steps I documented above.

Additional context.

[BawdyInkSlinger]

Completed