Update Ecosystem.markdown with scriptcs entry

1. Can you make REPL a link to a good page describing what a REPL is? Not everyone is familiar with the term.
2. Inconsistent casing on Scriptcs at the beginning of sentences - should the S be upper-cased or lower-cased if it's starting a sentence?
3. "Scriptcs also leverages for nuget extensibility" - I believe you meant "Scriptcs also leverages NuGet for extensibility"
4. Please case "nuget" as "NuGet"