Add "Hiring" section to readme.md (#3292)
Add "Hiring" section to readme.md (#3292)

* Add a "Hiring" section to readme.md

Added "QuantConnect is Hiring" to the top of the readme
Added links to the open roles on Indeed:
- Developer Advocate
- Quantitative Developer
- Quantitative Development Intern
StefanoRaggi/Lean,StefanoRaggi/Lean,JKarathiya/Lean,StefanoRaggi/Lean,jameschch/Lean,AlexCatarino/Lean,StefanoRaggi/Lean,QuantConnect/Lean,JKarathiya/Lean,QuantConnect/Lean,QuantConnect/Lean,jameschch/Lean,JKarathiya/Lean,AlexCatarino/Lean,jameschch/Lean,AlexCatarino/Lean,StefanoRaggi/Lean,QuantConnect/Lean,AlexCatarino/Lean,jameschch/Lean,jameschch/Lean,JKarathiya/Lean