docs: add installation section to readme

Author: vednoc

readme.org

@@ -6,3 +6,10 @@ that abstracts all the commonly used commands behind a simple a interface.
 Heavily inspired by:
 + [[https://github.com/lukrop/xbps-pkg][lukrop/xbps-pkg]]
 + [[https://www.freebsd.org/cgi/man.cgi?query=pkg&apropos=0&sektion=0&manpath=FreeBSD+12.1-RELEASE+and+Ports&arch=default&format=html][FreeBSD's pkg(8)]]
+
+** Installation
+Clone this repository, and make a symbolic link to ~pkg~ file in your ~$PATH~. E.g.:
+
+#+BEGIN_SRC shell
+ln -s /home/user/code/pkg/pkg /home/user/.local/bin
+#+END_SRC