Note how to get moreutils on FreeBSD (#1073)

Signed-off-by: Mateusz Piotrowski <0mp@FreeBSD.org>

text_collector_examples/README.md

@@ -10,6 +10,7 @@ To use these scripts, we recommend using a `sponge` to atomically write the outp
 Sponge comes from [moreutils](https://joeyh.name/code/moreutils/)
 * [brew install moreutils](http://brewformulas.org/Moreutil)
 * [apt install moreutils](https://packages.debian.org/search?keywords=moreutils)
+* [pkg install moreutils](https://www.freshports.org/sysutils/moreutils/)        
 
 For more information see:
 https://github.com/prometheus/node_exporter#textfile-collector