Tidy-up remaining TODOs

_for tracking_

The following TODOs exist in the codebase and need addressing:

- [ ] Directory.Build.targets: [`Include these in the shared space`](https://github.com/CommunityToolkit/Labs-Windows/blob/main/Directory.Build.targets#L14)
- [x] ReadMe.md ~[`Add info about copying template.`](https://github.com/CommunityToolkit/Labs-Windows/edit/main/ReadMe.md)~ - Addressed by #112
- [x] build.yml [`Detect experiments`](https://github.com/CommunityToolkit/Labs-Windows/blob/main/.github/workflows/build.yml#L57) | [`Detect experiments`](https://github.com/CommunityToolkit/Labs-Windows/blob/main/.github/workflows/build.yml#L132) - Addressed by #106
- [ ] ToolkitSampleMetadataGenerator.Documentation.cs
- [`Figure out line location`](https://github.com/CommunityToolkit/Labs-Windows/blob/main/common/CommunityToolkit.Labs.Core.SourceGenerators/ToolkitSampleMetadataGenerator.Documentation.cs#L53)
- [`Should generate the enum from these or something?`](https://github.com/CommunityToolkit/Labs-Windows/blob/main/common/CommunityToolkit.Labs.Core.SourceGenerators/ToolkitSampleMetadataGenerator.Documentation.cs#L109)
- [`extract index to get proper line number?`](https://github.com/CommunityToolkit/Labs-Windows/blob/main/common/CommunityToolkit.Labs.Core.SourceGenerators/ToolkitSampleMetadataGenerator.Documentation.cs#L123)
- [`extract index to get proper line number?`](https://github.com/CommunityToolkit/Labs-Windows/blob/main/common/CommunityToolkit.Labs.Core.SourceGenerators/ToolkitSampleMetadataGenerator.Documentation.cs#L135)
- [`Emit a better error that no documentation is here?`](https://github.com/CommunityToolkit/Labs-Windows/blob/main/common/CommunityToolkit.Labs.Core.SourceGenerators/ToolkitSampleMetadataGenerator.Documentation.cs#L202)
- [`Add list of sample ids in document`](https://github.com/CommunityToolkit/Labs-Windows/blob/main/common/CommunityToolkit.Labs.Core.SourceGenerators/ToolkitSampleMetadataGenerator.Documentation.cs#L231)
- [ ] ToolkitSampleMetadataGenerator.Sample.cs [`Emit a better error that no samples are here?`](https://github.com/CommunityToolkit/Labs-Windows/blob/main/common/CommunityToolkit.Labs.Core.SourceGenerators/ToolkitSampleMetadataGenerator.Sample.cs#L142)
- [ ] ToolkitSampleMetadataTests.cs [`We should have this return the references to the registries or something so we can check the generated output?`](https://github.com/CommunityToolkit/Labs-Windows/blob/main/common/CommunityToolkit.Labs.Core.SourceGenerators.Tests/CommunityToolkit.Labs.Core.SourceGenerators.Tests/ToolkitSampleMetadataTests.cs#L334)
- [X] ToolkitDocumentationRenderer.xaml [`Display Header for name of sample?`](https://github.com/CommunityToolkit/Labs-Windows/blob/main/common/CommunityToolkit.Labs.Shared/Renderers/ToolkitDocumentationRenderer.xaml#L22)