Initial draft for 0.94 release note (#41439)

This pull request updates the `README.md` to document the PowerToys 0.94
release. It includes comprehensive updates to release notes, download
links, and roadmap details, reflecting new features, improvements, and
fixes across multiple modules. The changes also improve documentation
for developers and update future planning information.

Release documentation and download updates:
* Updates all download links, release references, and installer
filenames from version 0.93 to 0.94 throughout the `README.md` to ensure
users get the latest release.
* Revises the release notes to highlight major new features (like
installer upgrade to WiX 5, settings search, hotkey conflict detection,
and module-specific enhancements), and reorganizes the changelog for
clarity.
* Updates the roadmap and "What's Next" section to reflect plans for
version 0.95 and beyond, including new features and ongoing work.

Module and feature highlights:
* Adds or expands sections for Always On Top, Hosts File Editor, Image
Resizer, Mouse Without Borders, and PowerRename, summarizing key
improvements and new options in each.
* Details significant Command Palette improvements, including
accessibility, stability, UI tweaks, and extension updates.

Developer and documentation improvements:
* Adds new documentation for building and testing the installer, fixes
broken links, and updates developer guidance for building modules and
using the test suite.
* Summarizes development process improvements, such as updated
dependencies, improved test coverage, and CI enhancements.

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Co-authored-by: Niels Laute <[email protected]>