feat: add ffmpeg-builds binary mirror (#879)

[skip ci]

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **New Features**
* FFmpeg builds are now available as a supported binary source, offering
static builds for Windows and Linux platforms (x86_64). Both master
branch and latest release versions are accessible.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

config/binaries.ts

@@ -955,6 +955,13 @@ const binaries = {
     repo: 'microsoft/ripgrep-prebuilt',
     distUrl: 'https://github.com/microsoft/ripgrep-prebuilt/releases',
   },
+  'ffmpeg-builds': {
+    category: 'ffmpeg-builds',
+    description: 'Static Windows (x86_64) and Linux (x86_64) Builds of ffmpeg master and latest release branch.',
+    type: BinaryType.GitHub,
+    repo: 'KarinJS/FFmpeg-Builds',
+    distUrl: 'https://github.com/KarinJS/FFmpeg-Builds/releases',
+  },
 } as const;
 
 export interface BinaryTaskConfig {