Replaced obsolete Gitter badge with Slack (#5031)
Replaced obsolete Gitter badge with Slack (#5031)


JKarathiya/Lean,StefanoRaggi/Lean,StefanoRaggi/Lean,jameschch/Lean,QuantConnect/Lean,jameschch/Lean,JKarathiya/Lean,QuantConnect/Lean,StefanoRaggi/Lean,StefanoRaggi/Lean,JKarathiya/Lean,AlexCatarino/Lean,QuantConnect/Lean,JKarathiya/Lean,AlexCatarino/Lean,jameschch/Lean,AlexCatarino/Lean,StefanoRaggi/Lean,QuantConnect/Lean,jameschch/Lean,jameschch/Lean,AlexCatarino/Lean