v1.23.1: Fix LESS_TERMCAP_xx handling

It was broken in 1.23.0.

v1.23.0: Different default style on bright terminal backgrounds

With this release, moar will check the terminal background color and
pick a different default style if the background is bright.

When viewing 24 bit colored text on a 256 color terminal, color
downsampling will now be somewhat more accurate.

Some CLI usability improvements were done. If the command line is wrong,
moar will now no longer print the full help text. This should make it
more obvious what went wrong.

For people using the LESS_TERMCAP_xx compatibility environment
variables:
* They are now visible in --help output
* They are rendered in --help output if they are valid
* They are highlighted in --help output if they are invalid
* --debug will now include a message if they are invalid

v1.22.3: Fix issue with -quit-if-one-stream

Before this release it didn't work for piped input.

v1.22.2: Render man page headings as GenericHeadings

This makes man pages nicer to read out of the box.

Other minor changes in this release:
* Use 16M color themes when requested, used to be 8 color themes (oops)
* Print less text on bad command lines to make the error message easier
  to find
* Render non-breaking spaces, we used to treat them as non-printable

v1.22.1: Fix issues with searching backwards

One hang and one not-found issue fixed.

v1.22.0: Add support for marking and jumping

In this release you can mark a position by pressing m (plus a label)
and then come back to it by pressing single quote (') plus the label.

Also, this release supports transparently decompressing zstd streams.

Plus internal re-arrangements of the code to make it easier to work
with.

v1.21.0: Add -lang option for setting highlight language

This will enable you to get syntax highlighting for piped input, or for
shell scripts which sometimes come without a file extension.

Also, in this release moar will default to select mouse mode in WezTerm.

v1.20.0: Improve color handling

With this release, it's possible to view 24 bit color text on 16 color
terminals, since we downsample colors that are too complex for the
current terminal.

Additionally this release improves mouse scrolling in some terminals and
prevents scrolling right into infinity.

v1.19.0: Make mouse both scroll and mark in some terminals

Some terminals will convert mouse wheel events to arrow key events, and
on those we don't really need our mouse support (which implicitly
disables the ability to mark text with the mouse).

With this release, for terminals which are known to do this we
automatically disable our built-in mouse support.

See also: https://github.com/walles/moar/issues/53

v1.18.6: Fix hyperlink rendering

Before this release, hyperlinks sometimes didn't get terminated, and
after exiting moar your whole screen would become hyperlinked.

Also, some search performance improvements went into this release.