This mode-line may have bugs and its implementation details are certain
to change (it doesn't follow naming conventions, for instance). It also
doesn't have all the features of the old modeline (yet).
However, it is easily twice as fast as the original, and a little more
flexible, what with the `mode-line-format-left' and
`mode-line-format-right' variables. It also exposes a more powerful API
for defining modelines and modeline segments (and switching between
them).
It is disabled by default and must be activated with the +new module
flag on the ui/doom-modeline module.
