Ruby: Add change note

Author: hmac

ruby/ql/lib/change-notes/2023-03-13-sinatra.md

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+---
+ category: minorAnalysis
+---
+* Accesses of `params` in Sinatra applications are now recognised as HTTP input accesses.
+* Data flow is tracked from Sinatra route handlers to ERB files.
+* Data flow is tracked between basic Sinatra filters (those without URL patterns) and their corresponding route handlers.