Support triple-quoted notation

Add support to triple-quoted notation (https://www.baeldung.com/kotlin-string-template):
+ Without escapes
ex.:
```kotlin
val path = """C:\Dir1\Dir2"""
```

+ Multi-line
```kotlin
val msg = """Item 1: $1.00
Item 2: $0.50"""
```

+ Internal quotemark
```kotlin
val str = """The field "abc" is readonly"""
```

