💥 feat!: add tag filtering for projects (#431)

- Card (project) images no longer require manual top/bottom margin
adjustments for proper spacing. Action needed: Review existing card
images as previous manual margin adjustments may now be
unnecessary/excessive.
- Sites using `cards.html` with tags will now load JavaScript by
default when tags are present. To maintain no-JS behaviour, explicitly
set `enable_cards_tag_filtering = false` in either `config.toml` or the
`_index.md` file where `cards.html` is used.

templates/page.html

@@ -61,6 +61,7 @@ Current section extra: {% if current_section %}{{ current_section.extra | json_e
 </pre></div>
 
     {% set settings_to_test = [
+        "enable_cards_tag_filtering",
         "footnote_backlinks",
         "add_src_to_code_block",
         "force_codeblock_ltr",