update: add multidollar interpolation to the list of proposals (#4448)

Author: koshachy

docs/topics/kotlin-language-features-and-proposals.md

@@ -251,6 +251,24 @@ guided by pragmatic design.
 
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+**KEEP discussion**
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+**Multidollar interpolation: improved handling of `$` in string literals**
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+* KEEP proposal: [dollar-escape.md](https://github.com/Kotlin/KEEP/blob/master/proposals/dollar-escape.md)
+* YouTrack issue: [KT-2425](https://youtrack.jetbrains.com/issue/KT-2425)
+* Target version: 2.1.0
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