Show breadcrumbs on mobile too

[chalin]

• Closes Show breadcrumbs on mobile #780
• Contributes to Cleanup: don't hard-code styles into layouts #783 -- note that the equivalent of the d-print-none was moved into the style definition so that clients can override this behavior if they so choose.
• Contributes to Clean up layouts/partials/breadcrumb.html #782

Preview, for example visit the following links on mobile or in a browser with a narrow window:

• https://deploy-preview-784--docsydocs.netlify.app/docs
• https://deploy-preview-784--docsydocs.netlify.app/docs/adding-content/shortcodes

For a screenshot, see below.

No net change in the generated site files except for the nav's change in class styles, whitespace being trimmed, and the new style definition:

$ npm run build
...
$ (cd public && git diff -bw --ignore-blank-lines -I 'class="(td-breadcrumbs|d-none d-md-block d-print-none)"' -- . ':(exclude)*.xml' ':(exclude)*.map')
... see below for the syntax-highlighted diff ...

diff --git a/scss/main.css b/scss/main.css
index 5fcf278..b8f8160 100644
--- a/scss/main.css
+++ b/scss/main.css
@@ -13797,8 +13797,12 @@ nav.foldable-nav .with-child ul {
   .btn-sm, .btn-group-sm > .btn {
     border-radius: 1rem; }
 
-.breadcrumb {
-  background: none;
+@media print {
+  .td-breadcrumbs {
+    display: none !important; } }
+
+.td-breadcrumbs .breadcrumb {
+  background: inherit;
   padding-left: 0;
   padding-top: 0; }

Screenshot

[chalin]

The only significant change here is the use of the td-breadcrumbs class. Every other change in the partial is a whitespace fix.

[chalin]

I'll take #780 (comment) as a thumbs up and merge this now. I'll add support for #781 before updating the docs.