add docs for squid cache parameters
add docs for squid cache parameters

Connects to #114
clearpathrobotics/buildfarm_deployment,ros-infrastructure/buildfarm_deployment,ros-infrastructure/buildfarm_deployment,ros-infrastructure/buildfarm_deployment,clearpathrobotics/buildfarm_deployment,ros-infrastructure/buildfarm_deployment,clearpathrobotics/buildfarm_deployment