Modern browsers have a "dark mode" preference, which enables alternate
styles on web sites that support this.

This patch adds a dark color scheme, that is automatically activated
via a CSS @media query.

Older browsers that do not support color schemes will simply show the
light scheme, but possibly without syntax highlighting.

Note that filters that use color (such as source highlighters) and
logotypes may need to be updated to work with a black background!
See the updated files in the filters/ directory.

Signed-off-by: Samuel Lidén Borell <samuel@kodafritt.se>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

This addressed a non-existent background image and made the element
invisible. Drop the style and use something sane.

Signed-off-by: Christian Hesse <mail@eworm.de>

This allows for cleaner nesting semantics and matches github more
closely.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

With sha1 we had a guaranteed length of 40 hex chars. This changes now
that we have to support sha256 with 64 hex chars... Support both.

Signed-off-by: Christian Hesse <mail@eworm.de>

luaossl has no upstream anymore and doesn't support OpenSSL 1.1,
whereas luaossl is quite active.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

This makes the markdown filter generate anchor links for headings.

Signed-off-by: Christian Hesse <mail@eworm.de>
Tested-by: jean-christophe manciot <actionmystique@gmail.com>

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

There's no use in giving a silly example to folks who will just copy it,
so instead try to do something slightly better.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

This is much better than having the user generate it themselves.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>