Adds installation instructions for FreeBSD to README

Signed-off-by: Tomás Senart <[email protected]>

Author: nrekretep

README.md

@@ -26,6 +26,14 @@ Or with [MacPorts](https://www.macports.org/):
 $ port install vegeta
 ```
 
+### FreeBSD
+
+On FreeBSD you can install Vegeta with the built in package manager because there is a [Vegeta Package](https://www.freshports.org/benchmarks/vegeta) available.
+
+```shell
+$ pkg install vegeta
+```
+
 ### Source
 
 ```shell