Jekyll Markdown syntax highlighting

Jekyll uses Markdown or HTML files to statically render complex websites from simple text files. While Jekyll syntax highlighting is possible, more often we might use more generic Markdown commands.

Enable syntax highlighting: Before every code block, simply include the language name, for example

{% raw %}

{% endraw %}

this even works for `gdb`.

The color code syntax highlighting on your webpage looks quite striking, and the number of languages covered is very extensive.
Despite the different syntax highlighter modules used by different Jekyll web hosting services, almost every language works with the method above.

## Notes

* Github uses [Linguist syntax highlighting](https://github.com/github/linguist/blob/master/lib/linguist/languages.yml) for its own service (Issues, README.md, etc.)
* Github/Gitlab Pages can use Rouge syntax highlighting via Jekyll `_config.yml` -- specify an allowed syntax highlighter.