Port to mdbook (#52)

* mdbook port
* implement figure numbering preprocessor, fix image links
* timers.md: mdBook compatible TOC and links
* update SUMMARY.md
* fix links/toc for dma.md, interrupts.md, swi.md
* content: fix markdown-in-html
* add note about img tags

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Co-authored-by: Antonio Vivace <avivace4@gmail.com>

Author: LunarLambda

.gitattributes

@@ -0,0 +1,8 @@
+*           text=auto
+Cargo.lock  -diff
+*.css       text
+*.htm       text
+*.html      text
+*.md        text
+*.jpg       binary
+*.png       binary

.github/workflows/deploy.yml

@@ -1,2 +1,2 @@
-__pycache__
-output
+/output/
+target/

.gitignore

@@ -0,0 +1,6 @@
+[submodule "mdbook-external-links"]
+	path = mdbook-external-links
+	url = https://github.com/jonahgoldwastaken/mdbook-external-links
+[submodule "mdbook-toc"]
+	path = mdbook-toc
+	url = https://github.com/badboy/mdbook-toc