Add feature for Map.prototype.getOrInsert() (#3360)

Co-authored-by: Patrick Brosset <patrickbrosset@gmail.com>

Author: ddbeck

features/getorinsert.yml

@@ -0,0 +1,8 @@
+name: Map getOrInsert()
+description: The `getOrInsert()` and `getOrInsertComputed()` methods of `Map` objects get a value, setting and getting a default value if needed.
+spec: https://tc39.es/proposal-upsert/
+compat_features:
+  - javascript.builtins.Map.getOrInsert
+  - javascript.builtins.Map.getOrInsertComputed
+  - javascript.builtins.WeakMap.getOrInsert
+  - javascript.builtins.WeakMap.getOrInsertComputed

features/getorinsert.yml.dist

@@ -0,0 +1,11 @@
+# Generated from: getorinsert.yml
+# Do not edit this file by hand. Edit the source file instead!
+
+status:
+  baseline: false
+  support: {}
+compat_features:
+  - javascript.builtins.Map.getOrInsert
+  - javascript.builtins.Map.getOrInsertComputed
+  - javascript.builtins.WeakMap.getOrInsert
+  - javascript.builtins.WeakMap.getOrInsertComputed