Update scripting.md script package sample
Update scripting.md script package sample

Update the sample code for "Creating A Script Package" to use
`robot.load`. Previously it was duplicating the `exists`/`readdir` logic
that `robot.load` already has, except it was doing the exists check
asynchronously, which changes script load order and also means the
script won't have loaded in time when using the `--config-check` flag.
michaelansel/hubot,melexis/melexis-hubot,lukw00/hubot,davidkassa/hubot,RiddickSky/hubot,rlugojr/hubot,jianchen2580/hubot,PropertyUX/nubot,PropertyUX/nubot,github/hubot,wyncode/hubot,craig5/hubot,brodul/hubot,scboucher/hubot,fgbreel/hubot,mujiansu/hubot,ouadie-lahdioui/hubot,krahman/hubot,AlexandrPuryshev/hubot,hubotio/hubot,lisb/hubot,howprice/hubot,blackwellops/hubot,Hartmarken/hubot,Mattlk13/Hubot,sdimkov/hubot,ddmng/brazil82-hubot,wieden-kennedy/hubot,joshsobota/hubot,chadfurman/hubot,skcript/skubot,Arthraim/merlin,bradparks/hubot__github_chat_bot,poppingtonic/hubot,msound/hubot,nandub/hubot,mutewinter/hubot,eetuuuu/hubot,ajayanandgit/hubot,codydaig/hubot,edorsey/hubot,hcxiong/hubot,vkhang55/hubot,aslihandincer/hubot,rafaell-lycan/Hubot-X9,WaleedAshraf/hubot,voltsdigital/hubot,mjurczyk/hubot,ajschex/hubot,minted/hubot,decaffeinate-examples/hubot,mrb/hubot,RavenB/hubot,CobyR/hubot,gregkare/hubot,GrimDerp/hubot,leohmoraes/hubot,kristenmills/hubot,lisb/hubot,eshamow/gutterbot,makii42/hubot,mauricionr/hubot,shinvdu/hubot,lisb/hubot,github/hubot,ClaudeBot/hubot,iDTLabssl/hubot,jasonkarns/hubot,Snorlock/hubot,bgranberry/hubot,nandub/hubot,danielcompton/hubot,keyvanakbary/hubot,alex-zhang/hubot,limianwang/hubot,cycomachead/hubot,hubotio/hubot,ykelvis/hubot,plated/hubot,pchaigno/hubot,jasonrhodes/botzero,kkirsche/hubot,zvelo/hubot,hotrannam/hubot,dopeboy/hubot,mcanthony/hubot,taojuntjpp/hubot,sharabash/hubot,fstehle/hubot,daudich/hubot,scboucher/hubot,alucardzhou/hubot,kgrz/hubot,mchill/hubot,geoffreyanderson/hubot,decaffeinate-examples/hubot,jschell/hubot,Drooids/hubot,ooohiroyukiooo/hubot,awbauer/hubot,julianromera/hubot,tiagochiavericosta/hubot,doudoupower/hubot