manual: use modified "haddock.theme" for nicer syntax highlighting;

use `tcolorbox` instead of `framed` for latex code blocks, works
  much better, especially as now when using a background colour;
  reduce gap after figures and force footnotes to bottom of page;
  move most symbology figures to after some text to lessen chance
  of subsection headers being orphaned on their own at end of page:
  required a number of rewordings;
  use named barcodes in example commands, rather than numbered;
  fix "lua-crossrefs" filter to allow parentheses around
  references;
  various other fixes and rephrasings

docs/lua-crossrefs/.luacheckrc

@@ -0,0 +1,13 @@
+stds.pandoc = {
+   read_globals = {
+      'FORMAT',
+      'pandoc',
+      'PANDOC_VERSION',
+   },
+
+   globals = {
+      'Pandoc',
+   },
+}
+
+std = 'lua54+pandoc'