Classes of the attributes like appearance='filled' for Input components don't persist

[vertonghenb]

For every Input component there is an annoying problem due to the way FAST currently handles the styling of the Web Components (using css classes). Since we cannot get access to the css classes FAST puts on the components after you've specified for example appearance='filled' on a TextArea. Since the classes are not there on the first render and later it gets pretty complicated and perf. intensive to get the classes.

The issue will be resolved by the core library, they'll switch to attribute based styling instead of class based styling which will solve this issue as discussed on Discord.

• [x] https://github.com/microsoft/fast/issues/4076
• [ ] microsoft/fluentui#15747

[vertonghenb]

Fixed for fast Todo Fluent