add "available since tact 1.6"

docs/src/content/docs/book/functions.mdx

@@ -138,6 +138,10 @@ contract Treasure {
 }
 ```
 
+### Explicit resolution of method ID collisions
+
+<Badge text="Available since Tact 1.6" variant="tip" size="large"/>
+
 As other functions in TVM contracts, getters have their *unique* associated function selectors which are some integers ids (called *method IDs*).
 Some of those integers are reserved for internal purposes, e.g. -4, -3, -2, -1, 0 are reserved IDs and 
 regular functions (internal to a contract and not callable from outside) are usually numbered by subsequent (small) integers starting from 1.