ArduinoJson 6.20.0 * Add `JsonVariant::shallowCopy()` (issue #1343) * Fix `9.22337e+18 is outside the range of representable values of type 'long'` * Fix comparison operators for `JsonArray`, `JsonArrayConst`, `JsonObject`, and `JsonObjectConst` * Fix lax parsing of `true`, `false`, and `null` (issue #1781) * Remove undocumented `accept()` functions * Rename `addElement()` to `add()` * Remove `getElement()`, `getOrAddElement()`, `getMember()`, and `getOrAddMember()` * Remove undocumented `JsonDocument::data()` and `JsonDocument::memoryPool()` * Remove undocumented `JsonArrayIterator::internal()` and `JsonObjectIterator::internal()` * Rename things in `ARDUINOJSON_NAMESPACE` to match the public names * Add documentation to most public symbols * Remove support for naked `char` (was deprecated since 6.18.0)