Add Gesture Recognition example (#5241)

Use the MediaPipe Gesture detection and Gesture landmark detection
solutions to track hands and recognise gestures in images and videos.

### Checklist
* [x] I have read and agree to [Contributor
Guide](https://github.com/rerun-io/rerun/blob/main/CONTRIBUTING.md) and
the [Code of
Conduct](https://github.com/rerun-io/rerun/blob/main/CODE_OF_CONDUCT.md)
* [x] I've included a screenshot or gif (if applicable)
* [x] I have tested the web demo (if applicable):
* Using newly built examples:
[app.rerun.io](https://app.rerun.io/pr/5241/index.html)
* Using examples from latest `main` build:
[app.rerun.io](https://app.rerun.io/pr/5241/index.html?manifest_url=https://app.rerun.io/version/main/examples_manifest.json)
* Using full set of examples from `nightly` build:
[app.rerun.io](https://app.rerun.io/pr/5241/index.html?manifest_url=https://app.rerun.io/version/nightly/examples_manifest.json)
* [x] The PR title and labels are set such as to maximize their
usefulness for the next release's CHANGELOG
* [x] If applicable, add a new check to the [release
checklist](https://github.com/rerun-io/rerun/blob/main/tests/python/release_checklist)!

- [PR Build Summary](https://build.rerun.io/pr/5241)
- [Docs
preview](https://rerun.io/preview/a6eb3f1c3fc46a8b47cc15cceeffb90d9e3f49eb/docs)
<!--DOCS-PREVIEW-->
- [Examples
preview](https://rerun.io/preview/a6eb3f1c3fc46a8b47cc15cceeffb90d9e3f49eb/examples)
<!--EXAMPLES-PREVIEW-->
- [Recent benchmark results](https://build.rerun.io/graphs/crates.html)
- [Wasm size tracking](https://build.rerun.io/graphs/sizes.html)

---------

Co-authored-by: Emil Ernerfeldt <[email protected]>
Co-authored-by: Antoine Beyeler <[email protected]>

docs/cspell.json

@@ -323,6 +323,7 @@
     "spaceviews",
     "spammy",
     "srcset",
+    "SRGB",
     "stacklevel",
     "startswith",
     "staticmethod",
@@ -344,6 +345,7 @@
     "timeseries",
     "tinyvec",
     "Tpng",
+    "tqdm",
     "trackpad",
     "trimesh",
     "Trimesh",

examples/manifest.toml

@@ -20,6 +20,7 @@ examples = [
   "dicom_mri",
   "face_tracking",
   "human_pose_tracking",
+  "gesture_detection",
   "lidar",
   "live_camera_edge_detection",
   "live_depth_sensor",

examples/python/gesture_detection/.gitignore

@@ -0,0 +1,2 @@
+dataset/hand_gestures
+/model