Add README for QuickLook.Plugin.InsvBlocker

Co-authored-by: emako <24737061+emako@users.noreply.github.com>

QuickLook.Plugin/QuickLook.Plugin.InsvBlocker/README.md

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+# QuickLook.Plugin.InsvBlocker
+
+This plugin prevents QuickLook from handling `.insv` files (Insta360 panoramic video files).
+
+## Purpose
+
+Insta360Studio has its own QuickLook application with the same name and activation method (pressing spacebar). When both applications are installed, pressing space on `.insv` files would cause both QuickLook windows to appear, creating a conflict.
+
+This plugin solves that issue by having QuickLook claim the file (via high priority) but immediately close without displaying anything, allowing Insta360Studio's QuickLook to handle the file instead.
+
+## Implementation
+
+- **Priority**: `int.MaxValue` (highest priority, checked before all other plugins)
+- **Behavior**: 
+  - Returns `true` for `CanHandle()` on files with `.insv` extension
+  - Sets minimal window size (1x1 pixels) in `Prepare()`
+  - Closes the window immediately in `View()` using `DispatcherPriority.Send`
+
+## Technical Details
+
+The plugin prevents the QuickLook window from becoming visible by:
+1. Matching `.insv` files with highest priority
+2. Setting a minimal window size to reduce visual impact if window briefly appears
+3. Closing the window immediately after content is set, before it becomes visible to the user
+
+This approach ensures that Insta360Studio's QuickLook can handle the file without interference.