Add WacomScrollFlow 0.1.3 plugin

[HollisMeynell]

Adds WacomScrollFlow, a pen scrolling plugin for OpenTabletDriver 0.6.7 or later.

Features

• Hold a configurable pen or tablet button to scroll while keeping the cursor fixed.
• Switch to horizontal scrolling when horizontal movement exceeds 100 pixels and is more than three times vertical movement.
• Suppress accidental tip clicks after button release until the pen is lifted.
• Press the button again before lifting to resume scrolling.
• Configure scrolling speed and reverse each axis independently.

Compatibility and validation

• Uses OpenTabletDriver's scrolling interface for Windows, Linux, and macOS.
• Supports standard Absolute Mode and Relative Mode through two filters: Scroll Flow: Input and Scroll Flow: Cursor Lock.
• Build and 24 automated tests pass on all three platforms.
• Release ZIP contains the plugin DLL at its root; SHA256 verified against the published archive.
• Licensed under MIT-0.

[Kuuuube]

Use case appears to already be covered by existing scroll plugin.