convert 24. The Lab to Markdown (#85)

* apply automatic conversion to 24. The Lab

Commands applied:

git mv lab.htm lab-old.htm
pandoc --from=html --to=markdown-fenced_divs-bracketed_spans-escaped_line_breaks-smart --wrap=none -o lab.md lab-old.htm
sed -i -E 's,^\s+$,,' lab.md
sed -i -E 's,<span class="dfn">([^<]+)</span>,<dfn>\1</dfn>,g' lab.md
sed -i -E 's,<span class="kbd">([^<]+)</span>,<kbd>\1</kbd>,g' lab.md
sed -i -E 's,^(##+) [0-9]+\.[0-9.]+,\1,g' lab.md
sed -i -E 's,\{target="_blank"\},,g' lab.md

* manual cleanup of 24. The Lab

- add to SUMMARY.md
- language for code snippets
- restore HTML for figs, tables, and equations and autonumber them
- convert 1 equation to MathML via LaTeX
- italic filenames

fix #63

content/SUMMARY.md

@@ -34,7 +34,7 @@
 - [More Mode7 tricks](./mode7ex.md)
 - [Tonc's Text Engine]()
 - [Whirlwind tour of ARM assembly](./asm.md)
-- [The Lab]()
+- [The Lab](./lab.md)
 
 ---