Add bootstrap-Arch.sh

usage: ./bootstrap-Arch.sh [-h] [-y]

Bootstrap an Arch Linux based distribution with:

* update pacman database
* upgrade pacman packages
* git - from pacman
* python-pip - from pacman
* python-virtualenv - from pacman
* SSH key - from ssh-keygen
* GitHub public key - with SSH key
* GitLab public key - with SSH key
* BitBucket Cloud public key - with SSH key
* Gogs public key - with SSH key
* conduit - configuration manager

If any already exist they will not be reinstalled.

optional arguments:
         -h             show this help message and exit
         -y             assume yes when prompted

README.md

@@ -16,6 +16,12 @@ To bootstrap a Debian based Linux instance:
 $ wget https://code.infektor.net/config/bootstrap/raw/master/bootstrap-Debian.sh && chmod +x bootstrap-Debian.sh && ./bootstrap-Debian.sh
 ```
 
+To bootstrap a Arch Linux based instance:
+
+```console
+$ curl -O https://code.infektor.net/config/bootstrap/raw/master/bootstrap-Arch.sh && chmod +x bootstrap-Arch.sh && ./bootstrap-Arch.sh
+```
+
 To bootstrap a Windows instance:
 
 ```console