feat(plugins): add term_tab plugin to complete other zsh sessions' directories (#3018)

plugins/term_tab/README

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+
+term_tab - 'cwd' for all open zsh sessions
+******************************************
+
+What it does:
+*************
+This plugin allows to complete the 'cwd' of other Zsh sessions. Sounds
+complicated but is rather simple. E.g. if you have three zsh sessions open, in
+each session you are in a different folder, you can hit Ctrl+v in one session
+to show you the current working directory of the other open zsh sessions.
+
+How it works:
+*************
+* It uses 'pidof zsh' to determine all zsh PIDs
+* It reads procfs to get the current working directory of this session
+* Everything is fed into zsh's completion magic