docs: added maintainer documentation with FileSystemWatcherMock

[pw-sgr]

#926

• Add maintainer documentation directly into Docs
• Mention the maintainer documentation in CONTRIBUTING.md
• Add a link to the documentation file in the XML-Documentation of the FileSystemWatcherMock

[pw-sgr]

@vbreuss added the general outline and the mentioned events for the watcher. Maintainer.md will link to the individual mocks and have general documentation.

[Copilot]

Pull request overview

This PR adds maintainer documentation for the FileSystemWatcherMock implementation, documenting platform-specific behavior differences for file system events across Linux, Windows, and macOS.

Changes:

• Added comprehensive documentation tables showing FileSystemWatcher event behavior across different platforms
• Created maintainer documentation structure in the Docs folder
• Linked documentation from CONTRIBUTING.md and FileSystemWatcherMock class

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
Docs/FileSystemWatcherMock.md	Documents event behavior tables for FileSystemWatcher across platforms with and without subdirectory inclusion
Docs/Maintainer.md	Creates maintainer documentation index linking to implementation details
CONTRIBUTING.md	Adds reference to maintainer documentation for developers
Source/Testably.Abstractions.Testing/FileSystem/FileSystemWatcherMock.cs	Adds XML documentation remarks linking to the FileSystemWatcherMock documentation
Testably.Abstractions.sln	Includes new documentation files in the solution under the Docs project section

[vbreuss]

LGTM, thanks @pw-sgr

[github-actions]

This is addressed in release v5.1.0.