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., `dotfiles-install` and `dotfiles-update`)
- Add README.md with info on the installation and general notes

.bashrc

@@ -0,0 +1,14 @@
+#!/bin/bash
+
+# `bash`-specific configurations
+
+
+# Prevent running this file twice, as a non-login `bash` enters here,
+# sources ~/.profile, and ~/.profile sources this file again
+[ -n "$BASHRC_LOADED" ] && return
+BASHRC_LOADED=1
+
+
+# Load configuration files common to all kinds of shells,
+# if not already done by a `bash` login shell
+[ -z "$PROFILE_LOADED" ] && [ -f "$HOME/.profile" ] && . "$HOME/.profile"