Idler v0.1.1 — the OpenFX build

Ships the OpenFX build: the same eleven savers as a generator and a matching
filter for DaVinci Resolve, Nuke and Natron, in one bundle per platform.

An OFX host hands a plugin a buffer rather than a GL context, so that build
rasterises the scene in software. The savers themselves are the same code —
idtest --raster renders all eleven through both renderers and compares the
picture, and they agree at 100% coverage with a mean channel error under 0.0006.
Sync there offers Free and Manual only, because OFX carries no tempo; Phase is
the thing to keyframe.

Also fixes a mask default that was wrong in v0.1.0. The effect variant
defaulted to an opaque background, which covered the clip it exists to draw over
— Over looked like the effect had replaced the clip, and Reveal, Hide and
Colourise were all no-ops. The effect now defaults to a transparent background,
and presets leave the background alone on the effect for the same reason they
already leave Mask Mode alone.

Installing

• Resolume — the .dmg (macOS) or the -setup.exe (Windows), or drop the
  two bundles from idler-macos-universal.zip / idler-windows-x86_64.zip into
  your Extra Effects folder.
• Resolve, Nuke, Natron — idler-ofx-*.zip, into /Library/OFX/Plugins
  (macOS) or C:\Program Files\Common Files\OFX\Plugins (Windows).

macOS builds are signed with a Developer ID, notarised and stapled. The Windows
builds are unsigned, so SmartScreen warns once.

The OpenFX build has been loaded and rendered in a test host, but has never run
in Resolve, Nuke or Natron.

Built locally rather than in CI: GitHub Actions was in a major outage, with
webhook triggers throttled, when this was cut.