Add changelog for v0.8 pre-release: Introduce filament mixer color accuracy improvements, and installation instructions. Update README to include support for development. Enhance AboutDialog with updated application name and links.

CHANGELOG_v0.8.md

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+## v0.8 Pre-release
+
+EXPERIMENTAL BUILD - LIMITED TESTING
+Based on Snapmaker Orca v2.2.4
+
+v0.8 full spectrum pre-release focuses on filament mixer color accuracy and Linux AppImage packaging.
+
+This has had limited testing on the Snapmaker U1 via the community.
+
+### What's New in v0.8
+
+#### Filament Mixer Color Blending (v0.8)
+- Replaced the legacy RYB blend path with FilamentMixer.
+- Updated mixed-filament preview/display color computation to use FilamentMixer interpolation.
+- Improved mixed-filament color consistency for generated combinations.
+- Retained legacy RYB conversion helpers in code as reference.
+
+#### Linux AppImage Packaging (new in v0.8)
+- Added Linux release artifact: `Snapmaker_Orca_Linux_V2.2.4.AppImage`.
+- AppImage is now the primary Linux release artifact for end users.
+- Current Linux build target is `x86_64`.
+- Current runtime baseline is glibc `2.38+`.
+- `Snapmaker_Orca.tar` remains available as an advanced/manual fallback.
+
+### Installation
+
+#### Windows
+1. Download `Snapmaker_Orca.zip`.
+2. Extract to a folder.
+3. Run the executable.
+
+#### macOS
+1. Download the macOS build (`arm64` for Apple Silicon or `x86_64` for Intel).
+2. If the release asset is a `.zip`, unzip it first.
+3. Open the `.dmg`.
+4. Drag `Snapmaker_Orca.app` into `Applications`.
+5. Launch the app from `Applications`.
+
+#### Linux (AppImage)
+1. Download `Snapmaker_Orca_Linux_V2.2.4.AppImage`.
+2. Run `chmod +x Snapmaker_Orca_Linux_V2.2.4.AppImage`.
+3. Run `./Snapmaker_Orca_Linux_V2.2.4.AppImage`.
+
+### Warning
+- Use at your own risk.
+- May produce incorrect G-code in edge cases.
+- Mixed-filament behavior is still experimental in some scenarios.
+- This release has had limited real-printer validation.
+
+### Features Not Yet Fully Tested
+1. Linux AppImage behavior across all desktop environments/distributions.
+2. Mixed-filament visual color matching across different filament brands/materials.
+
+### Known Issues
+- Older Linux distributions may fail to run this AppImage due to glibc mismatch.
+- Some systems may require `libfuse2` for AppImage execution.
+- On-screen color blend preview may not exactly match physical print results.
+
+### Credits
+- FilamentMixer color blending integration is powered by the FilamentMixer library by [justinh-rahb](https://github.com/justinh-rahb).
+- Library repository: [https://github.com/justinh-rahb/filament-mixer](https://github.com/justinh-rahb/filament-mixer).