docs(term_tab): rewrite README in markdown (#11381)

plugins/term_tab/README → plugins/term_tab/README.md

+# term_tab plugin
 
-term_tab - 'cwd' for all open zsh sessions
-******************************************
+term_tab - `cwd` for all open zsh sessions
 
-What it does:
-*************
-This plugin allows to complete the 'cwd' of other Zsh sessions. Sounds
+## 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
+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
+## 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