Add configuration for zsh

- Add ~/.zshrc
  + Configure on how the `history` works
  + Enable nicer `cd` and globbing behavior
  + Enable tab completion, and make them feel nicer
  + Enable VI mode and add some VI-like key bindings
- Add ~/.zlogout clearing the screen
- Add ~/.config/zsh/.zshrc and make it dispatch to ~/.zshrc
  to make `zsh` use the same configuration even on more
  recent Debian/Ubuntu machines that do not look for
  ~/.zshrc any more
- Ensure ~/.local/state/zsh/ exists

.zshenv

@@ -0,0 +1,8 @@
+#!/bin/zsh
+
+# Sourced by `zsh` before /etc/zsh/zshrc,
+# and thus the only place where the following can be set in time
+
+# Otherwise, Debian's /etc/zsh/zshrc calls `compinit` without arguments,
+# which creates a second ~/.zcompdump next to the XDG one set in ~/.zshrc
+skip_global_compinit=1