Sample App Design Improvements

[michael-hawker]

Right now the Sample App is all structure, but we should make some functional improvements to its functionality and design.

### Essentials
- [x] Add theme selection
- [x] FlowDirection toggle
- [x] Light/Dark Theme toggle
- [ ] https://github.com/CommunityToolkit/Tooling-Windows-Submodule/issues/87
- [ ] https://github.com/CommunityToolkit/Tooling-Windows-Submodule/issues/85

### All components app:
- [X] Clean-up of overall documentation display, like side-panel for sample navigation and extra documentation metadata/github links, etc... (like the XAML Controls Gallery) [see comment here](https://github.com/CommunityToolkit/Labs-Windows/pull/85#discussion_r864255062)
- [X] CommunityToolkit/Tooling-Windows-Submodule#82 
- [X] Create a home/landing page
- [X] Add more about information

### Single component app:
  - [ ] Accessibility (see CommunityToolkit/Labs-Windows#86 as well)
  - [X] Headings for embedded Samples/Clean-up of Sample Display/Layout _[see comment here](https://github.com/CommunityToolkit/Labs-Windows/pull/85#discussion_r864254495)_
  - [ ] CommunityToolkit/Labs-Windows#67 

[mrlacey]

Is it appropriate to also add an option to change the language/culture? Doing so will make it easier to spot any localization issues.

[michael-hawker]

@mrlacey yeah, that's a good idea. Is that something we can dynamically change at runtime easily and get the XAML resources to update from?

[mrlacey]

@mrlacey yeah, that's a good idea. Is that something we can dynamically change at runtime easily and get the XAML resources to update from?

I'll investigate how well supported this is across platforms - I've heard differing things.

[Arlodotexe]

Is it appropriate to also add an option to change the language/culture? Doing so will make it easier to spot any localization issues.

Great idea. I'll add that we should have a switch for toggling RTL mode and light/dark mode per sample.

[michael-hawker]

Great idea. I'll add that we should have a switch for toggling RTL mode and light/dark mode per sample.

On the to do list above already. 😉

[michael-hawker]

Split out the specific Markdown rendering technical bit to CommunityToolkit/Labs-Windows#151.