Fix various style/template issues (#2103)

* Fix various style/template issues

- Add styles to allow fully invisible headers. These can be used to
  support anchor links in translated pages, so we can move the link_subs
  out of the dactyl-config.yml. Example in transaction-common-fields.md
- Upgrade jQuery to 3.7.1
- Add left nav to references landings for consistent navigation
- Add breadcrumbs template (previously used Dactyl built-in) which
  throws an error if you specify a parent: that doesn't exist.
  (Previously it would write a blank link; the link checker would
  report this as an error, but it wasn't obvious what the cause was.)
- Fix #2014 (special case for code blocks nested in lists).
- Fix #2096.
- Remove excessive spacing between top nav and main content, and
  re-align top of main contents in all 3 columns for docs pages.
- Reorganize _content.scss to be easier to read.

* Upgrade yarn packages (fix dependabot alerts) & rebuild CSS

* Fix NFT broken link in translation

* [ja] Properly fix NFT data link

styles/_content.scss

@@ -1,85 +1,109 @@
 /* Content text styling (applies mostly to Markdown-generated content)------- */
-// TODO: convert this to nested SCSS format
 
 .content {
   padding-bottom: 50px;
 
   p code,
   table code,
-  ul code,
-  ol code {
+  li > code {
     background-color: $green-1000;
     color: $green-400;
   }
+
+  a {
+    text-decoration: underline;
+  }
+
+  h1 {
+    font-size: 3rem;
+    margin-top: 32px;
+    line-height: 1.2;
+    font-weight: 700;
+
+    &:first-child {
+      margin-top: 0;
+      line-height: 1.2;
+
+      &::before {
+        margin-top: -80px;
+      }
+    }
+  }
+
+  h2 {
+    margin-top: 2.5rem;
+    margin-bottom: 1.5rem;
+    font-size: 2.5rem;
+    font-weight: 600;
+    line-height: 1.2;
+  }
+
+  h3 {
+    font-size: 2.125rem;
+    margin-top: 2rem;
+    margin-bottom: 1rem;
+    line-height: 1.2;
+  }
+
+  h4 {
+    font-size: 1.75rem;
+    margin-top: 1.5rem;
+    margin-bottom: 0.5rem;
+    line-height: 1.2;
+  }
+
+  h5 {
+    font-size: 1.25rem;
+    margin-top: 1.25rem;
+    line-height: 1.2;
+    font-weight: 700;
+  }
+
+  h6 {
+    font-size: 1rem;
+    margin-top: 1rem;
+    line-height: 1.2;
+    font-weight: 700;
+  }
+
+  /* Some list items contain <p> tags, some don't. These styles make sure both
+   kinds are spaced consistently. */
+  li {
+    margin: 6px;
+    margin-top: 24px;
+  }
+  li p {
+    margin: 0;
+  }
+
+  // "Source" links float right
+  a[title="Source"] {
+    float: right;
+    padding-left: 20px;
+  }
+
+  // Make "invisible" headers take up no space either, so we can use them
+  // to add additional anchors (e.g. for translated pages)
+  h1.invisible,
+  h2.invisible,
+  h3.invisible,
+  h4.invisible,
+  h5.invisible,
+  h6.invisible {
+    font-size: 0;
+    line-height: 0;
+    margin: 0;
+
+    .hover_anchor {
+      display: none;
+    }
+  }
 }
 
-.content a,
 .blurb a {
   text-decoration: underline;
 }
 
-.content h1 {
-  font-size: 3rem;
-  margin-top: 32px;
-  line-height: 1.2;
-  font-weight: 700;
-}
-.content h1:first-child,
-.landing section:first-of-type h1:first-child {
-  margin-top: 0;
-  line-height: 1.2;
-}
-.content h1:first-child:before {
-  margin-top: -80px;
-}
-.content h2 {
-  margin-top: 2.5rem;
-  margin-bottom: 1.5rem;
-  font-size: 2.5rem;
-  font-weight: 600;
-  line-height: 1.2;
-}
-.content h3 {
-  font-size: 2.125rem;
-  margin-top: 2rem;
-  margin-bottom: 1rem;
-  line-height: 1.2;
-}
-.content h4 {
-  font-size: 1.75rem;
-  margin-top: 1.5rem;
-  margin-bottom: 0.5rem;
-  line-height: 1.2;
-}
-.content h5 {
-  font-size: 1.25rem;
-  margin-top: 1.25rem;
-  line-height: 1.2;
-  font-weight: 700;
-}
-.content h6 {
-  font-size: 1rem;
-  margin-top: 1rem;
-  line-height: 1.2;
-  font-weight: 700;
-}
-
-/* Some list items contain <p> tags, some don't. These styles make sure both
-   kinds are spaced consistently. */
-.content li {
-  margin: 6px;
-  margin-top: 24px;
-}
-.content li p {
-  margin: 0;
-}
-
-/* "Source" links float right */
-.content a[title="Source"] {
-  float: right;
-  padding-left: 20px;
-}
-
 // Hover anchors ---------------
 .hover_anchor {
   visibility: hidden;