update: update the multi-dollar string interpolation docs (#4924)

* update: update the multi-dollar string interpolation docs
* fix: review

Author: koshachy

docs/topics/coding-conventions.md

@@ -865,12 +865,28 @@ Omit semicolons whenever possible.
 
 ### String templates
 
-Don't use curly braces when inserting a simple variable into a string template. Use curly braces only for longer expressions.
+Don't use curly braces when inserting a simple variable into a string template. Use curly braces only for longer expressions:
 
 ```kotlin
 println("$name has ${children.size} children")
 ```
 
+Use [multi-dollar string interpolation](strings.md#multi-dollar-string-interpolation)
+to treat the dollar sign chars `$` as string literals:
+
+```kotlin
+val KClass<*>.jsonSchema : String
+get() = $$"""
+    {
+      "$schema": "https://json-schema.org/draft/2020-12/schema",
+      "$id": "https://example.com/product.schema.json",
+      "$dynamicAnchor": "meta",
+      "title": "$${simpleName ?: qualifiedName ?: "unknown"}",
+      "type": "object"
+    }
+    """
+```
+
 ## Idiomatic use of language features
 
 ### Immutability

docs/topics/strings.md

@@ -161,13 +161,6 @@ ${'$'}_9.99
 
 ### Multi-dollar string interpolation
 
-> The multi-dollar string interpolation is [Experimental](components-stability.md#stability-levels-explained)
-> and opt-in is required (see details below).
-> 
-> It may be changed at any time. We would appreciate your feedback in [YouTrack](https://youtrack.jetbrains.com/issue/KT-2425).
->
-{style="warning"}
-
 Multi-dollar string interpolation allows you to specify how many consecutive dollar signs are required to trigger interpolation.
 Interpolation is the process of embedding variables or expressions directly into a string.
 
@@ -186,7 +179,7 @@ val KClass<*>.jsonSchema : String
     {
       "$schema": "https://json-schema.org/draft/2020-12/schema",
       "$id": "https://example.com/product.schema.json",
-      "$dynamicAnchor": "meta"
+      "$dynamicAnchor": "meta",
       "title": "$${simpleName ?: qualifiedName ?: "unknown"}",
       "type": "object"
     }
@@ -222,24 +215,7 @@ println(requestedData)
 
 Here, the `$$$` prefix allows the string to include `$` and `$$` without requiring the `${'$'}` construct for escaping.
 
-To enable the feature, use the following compiler option in the command line:
-
-```bash
-kotlinc -Xmulti-dollar-interpolation main.kt
-```
-
-Alternatively, update the `compilerOptions {}` block of your Gradle build file:
-
-```kotlin
-// build.gradle.kts
-kotlin {
-    compilerOptions {
-        freeCompilerArgs.add("-Xmulti-dollar-interpolation")
-    }
-}
-```
-
-This feature doesn't affect existing code that uses single-dollar string interpolation. 
+Multi-dollar string interpolation doesn't affect existing code that uses single-dollar string interpolation. 
 You can continue using a single `$`
 as before and apply multi-dollar signs when you need to handle literal dollar signs in strings.