Add changelog entry for isBasicType

See PR dlang#8838

changelog/PR8838.dd

@@ -0,0 +1,10 @@
+isBasicType!T now returns false for enum types
+
+In the language spec, a basic type is defined to be one of `void`, `bool`, a
+built-in integer type, a built-in character type, or a built-in floating-point
+type.
+
+Prior to this release, `isBasicType!T` returned `true` when `T` was either a
+basic type, or an `enum` type whose base type was a basic type. Now, it returns
+`false` for all `enum` types, and only returns `true` if `T` itself is a basic
+type.