Add terminal find matches

[OverHash]

Vscode needs some extra config set for the intergrated terminal ctrl+f to nicely show results. Currently, Plastic doesn't show the results that great (it's just like regular text, so impossible to see matches and the current selected match):

In this image, I had ctrl+f'd for "brew" and it's impossible to tell which "brew" I have selected, as the terminal does not show the match results well at all.

terminal.findMatchBackground
terminal.findMatchHighlightBackground
terminal.findMatchBorder
terminal.findMatchHighlightBorder
terminalOverviewRuler.findMatchForeground

could all be considered to be set.

[OverHash]

Example of what an improved terminal match could look like. Colors chosen semi-randomly here, but illustrates the value of adding these to the plastic config.

[will-stone]

Thanks! Would you like to open a PR? Try copying the editor find theme to see what it looks like?

https://github.com/will-stone/plastic/blob/main/src/colors.ts#L80