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

.config/zsh/README.md

@@ -0,0 +1,8 @@
+# `zsh`-related Configurations
+
+This folder is NOT read by `zsh` by default:
+    `zsh` only reads `$ZDOTDIR`, which defaults to ~/.
+
+The files here are failsafes:
+    Should some machine or future distribution set `$ZDOTDIR` to this folder,
+    they dispatch back to the real config files in ~/.