docs: Make lAtEX output *work*

pdflatex simply doesn't cut it.

This still results in an awkward pdf that starts with "Further
Reading" (the intro section is placed before it, but doesn't have a
chapter marker!) and ends with a massive "Other help pages" chapter
that includes *the entire rest of the docs*.

But it's generally readable and acceptably formatted (with a lot of
empty pages in between).

doc_src/conf.py

@@ -135,19 +135,14 @@ html_sidebars = {"**": ["globaltoc.html", "searchbox.html", "localtoc.html"]}
 
 # -- Options for LaTeX output ------------------------------------------------
 
+# The default font is "GNU FreeSans" or something which I've never heard of.
+# Make this something that might actually be installed.
 latex_elements = {
-    # The paper size ('letterpaper' or 'a4paper').
+    'fontpkg': r'''
-    #
+    \setmainfont{Noto Serif}
-    # 'papersize': 'letterpaper',
+    \setsansfont{Noto Sans}
-    # The font size ('10pt', '11pt' or '12pt').
+    \setmonofont{Noto Sans Mono}
-    #
+    ''',
-    # 'pointsize': '10pt',
-    # Additional stuff for the LaTeX preamble.
-    #
-    # 'preamble': '',
-    # Latex figure (float) alignment
-    #
-    # 'figure_align': 'htbp',
 }
 
 # Grouping the document tree into LaTeX files. List of tuples
@@ -163,6 +158,9 @@ latex_documents = [
     )
 ]
 
+# The default pdflatex doesn't handle unicode.
+# Switch to an engine that does (why pdflatex still exists and is still the default? I don't know)
+latex_engine = 'xelatex'
 
 # -- Options for manual page output ------------------------------------------