This mimics the backend logic for adding the data-attribute -
to know what Pygments language was used to highlight the code
block - in locally echoed messages.
New test added checks our logic for canonicalizing pygments alias
(for both frontend and backend).
Other fixtures and tests amended.
Since our Webpack config passes pre-minified JS files to
script-loader, they can’t be used as modules. Use the normal
unminified version, letting Webpack minify it and give us source maps.
Signed-off-by: Anders Kaseorg <anders@zulip.com>