[flang] Add David Truby as maintainer for Flang on Windows (llvm#142619)

Author: DavidTruby

flang/Maintainers.md

@@ -79,6 +79,13 @@ [email protected] (email), clementval (GitHub), clementval (Discourse)
 Abid Qadeer \
 [email protected] (email), abidh (GitHub), abidh (Discourse)
 
+### Platform maintainers
+These maintainers are responsible for particular platforms that Flang supports
+
+#### Windows
+David Truby \
+[email protected] (email), davidtruby (GitHub), davidtruby (Discourse), truby (Discord)
+
 ## Inactive Maintainers
 ### Lead Maintainers
 #### Backend : (Lowering, FIR, Codegen)