Add base configuration

- Follow XDG standard: ~/.config and ~/.local folders
- Set environment variables and define aliases within ~/.config/shell
- Add installation script for easy setup and maintenance
  (i.e., `install-dotfiles` and `update-dotfiles`,
   and a `ensure-locales` helper)
- Add README.md with info on the installation and general notes

.config/shell/locale

@@ -0,0 +1,24 @@
+#!/bin/sh
+
+# Locale settings for headless machines
+
+
+# Drop what a client may forward over `ssh`,
+# because `AcceptEnv LANG LC_*` may be set in /etc/ssh/sshd_config
+unset \
+    LC_ALL \
+    LC_ADDRESS \
+    LC_COLLATE \
+    LC_CTYPE LC_IDENTIFICATION \
+    LC_MEASUREMENT \
+    LC_MESSAGES \
+    LC_MONETARY \
+    LC_NAME \
+    LC_NUMERIC \
+    LC_PAPER \
+    LC_TELEPHONE \
+    LC_TIME
+
+
+# Set every LC_* category implicitly with the `$LANG` fallback
+export LANG=C.UTF-8