feat(plugins): add grc plugin for Generic Colouriser (#9315)

Co-authored-by: Marc Cornellà <marc.cornella@live.com>

plugins/grc/README.md

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+# Generic Colouriser plugin
+
+This plugin adds wrappers for commands supported by [Generic Colouriser](https://github.com/garabik/grc):
+
+To use it, add `grc` to the plugins array in your zshrc file:
+
+```zsh
+plugins=(... grc)
+```
+
+## Commands
+
+The following commands are wrapped by `grc` so that their output is automatically colored:
+
+- `cc`
+- `configure`
+- `cvs`
+- `df`
+- `diff`
+- `dig`
+- `gcc`
+- `gmake`
+- `ifconfig`
+- `iwconfig`
+- `last`
+- `ldap`
+- `make`
+- `mount`
+- `mtr`
+- `netstat`
+- `ping`
+- `ping6`
+- `ps`
+- `traceroute`
+- `traceroute6`
+- `wdiff`
+- `whois`