Fixed typo in build command
Fixed typo in build command

The build command specifies using composer.json as the build file. This should be something like config.json.

See the documentation on: https://getcomposer.org/doc/articles/handling-private-packages-with-satis.md

`php bin/satis build <configuration file> <build dir>`

The build command step on README.md and handling-private-packages-with-satis.md will be the same with this change.
Tyrael/satis,Leftbrained/satis,JamesRezo/satis,bartekmis/satis,ninjaparade/satis,bartekmis/satis,yonh/satis,achristodoulou/satis,MoT3rror/satis,gencer/satis,JamesRezo/satis,alcohol/satis,nfreear/satis,kavw/satis,ezsystems/satis,monsieurbiz/packages.monsieurbiz.com,astax-t/satis,gencer/satis,monsieurbiz/packages.monsieurbiz.com,nfreear/satis,alcohol/satis,socifi/satis,yonh/satis,phansys/satis,ezsystems/satis,JeroenDeDauw/satis,JeroenDeDauw/satis,Tyrael/satis,composer/satis,andkirby/satis,achristodoulou/satis,phansys/satis,alcohol/satis,alcohol/satis,composer/satis,ninjaparade/satis,kavw/satis,ezsystems/satis,MoT3rror/satis,composer/satis,socifi/satis,astax-t/satis,andkirby/satis,Leftbrained/satis,andkirby/satis,gencer/satis,monsieurbiz/packages.monsieurbiz.com