[FR] new TUI features such as regex syntax highlighting

Work in progress TUI additions for upcoming release 4.3.1:

make Tab navigation to directories and files also work when command line FILE arguments are present (✅ done)
make CTRL-Y file view work for standard input searched (✅ done)
make CTRL-Y file view work for files stored in archives by piping a decompressed file to the viewer (✅ done)
syntax highlight regular expression patterns in the TUI with user-definable colors (✅ done)

Planned for release after Oct 18.

Example regex syntax highlighting in the TUI with the default color scheme:

The user-definable TUI colors are defined in the same way the GREP_COLORS and --colors=COLORS are set with the following new parameters, which are all optional (when not specified the default is used):

param	result
`qp=`	TUI prompt
`qe=`	TUI errors
`qr=`	TUI regex
`qm=`	TUI regex meta characters
`ql=`	TUI regex lists and literals
`qb=`	TUI regex braces

Genivia / ugrep

[FR] new TUI features such as regex syntax highlighting #300