added countdown tones based on convar created in readyup.sp
define the necessary variables so that we don't have a dependency on readyup.sp being loaded
Merge pull request #12 from rpdelaney/feature/pause-countdown-sounds

Feature/pause countdown sounds
copied documentation for convars shared between readyup.sp and pause.sp
Merge pull request #13 from rpdelaney/feature/pause-countdown-sounds

copied documentation for convars shared between readyup.sp and pause.sp