Add 16 colour mode

[tombh]

Currently Browsh only supports 2 colours and 16 million colours. This is a little extreme, there are many, many scenarios in which 16 colour support would offer a massive improvement over either ugly banding lines or monochrome mode.

[jxyzn]

88-color and 256-color modes would also be really nice to have.

[datamaskinen]

This is the most important to make it fully usable in a unix terminal ... keep up the good work dude

[tobimensch]

@jxyzn @datamaskinen
It looks like 256 color mode already works, if you set the following environment variable, before starting browsh:
export TCELL_TRUECOLOR=disable

This disables truecolor support explicitly, and it seems to fall back to 256 colors in my experiments inside a tmux session.

It does also get rid of the ugly vertical lines.

I'm not sure, if this causes any side issues, it would be great if you could give this workaround a go and report your experiences with it.

In theory this should make browsh usable on a huge range of terminals.

@tombh
Did you know this workaround?

[tobimensch]

Even better, it looks like 16 color mode also is relatively easy to achieve.

I just had to replace "xterm-truecolor" in interfacer/src/browsh/browsh.go with "linux" in line 181.

This also makes browsh look usable on the bare linux console for the first time.

I don't know what showstoppers there may be that make this mode not really usable, but it's worthwhile to try this simple change.

It does also appear to lower bandwidth requirements, like it should.

brow.sh looked decent in this mode.

[tombh]

Nice detective work! This is such good news. It looks like we can really extend Browsh's compatibility with just a few updates :)