ArduinoJson 6.5.0-beta * Added implicit conversion from `JsonArray` and `JsonObject` to `JsonVariant` * Allow mixed configuration in compilation units (issue #809) * Fixed object keys not being duplicated * `JsonPair::key()` now returns a `JsonKey` * Increased the default capacity of `DynamicJsonDocument` * Fixed `JsonVariant::is<String>()` (closes #763) * Added `JsonArrayConst`, `JsonObjectConst`, and `JsonVariantConst` * Added copy-constructor and copy-assignment-operator for `JsonDocument` (issue #827)