Fix: Add video/mp4 to MediaType (rerun-io#7317)

### What

- Add `video/mp4` to `MediaType` in all languages
- Fix media type guessing

### 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)
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* Using examples from latest `main` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/7317?manifest_url=https://app.rerun.io/version/main/examples_manifest.json)
* Using full set of examples from `nightly` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/7317?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)!
* [x] If have noted any breaking changes to the log API in
`CHANGELOG.md` and the migration guide

- [PR Build Summary](https://build.rerun.io/pr/7317)
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crates/store/re_types/src/components/media_type_ext.rs

@@ -45,6 +45,11 @@ impl MediaType {
     /// Either binary or ASCII.
     /// <https://www.iana.org/assignments/media-types/model/stl>
     pub const STL: &'static str = "model/stl";
+
+    /// [MP4 video](https://en.wikipedia.org/wiki/MP4_file_format): `video/mp4`.
+    ///
+    /// <https://www.iana.org/assignments/media-types/video/mp4>
+    pub const MP4: &'static str = "video/mp4";
 }
 
 impl MediaType {
@@ -101,6 +106,12 @@ impl MediaType {
     pub fn stl() -> Self {
         Self(Self::STL.into())
     }
+
+    /// `video/mp4`
+    #[inline]
+    pub fn mp4() -> Self {
+        Self(Self::MP4.into())
+    }
 }
 
 impl MediaType {

rerun_cpp/src/rerun/components/media_type_ext.cpp

@@ -79,6 +79,13 @@ namespace rerun {
                 return "model/stl";
             }
 
+            /// [MP4 video](https://en.wikipedia.org/wiki/MP4_file_format): `video/mp4`.
+            ///
+            /// <https://www.iana.org/assignments/media-types/video/mp4>
+            static MediaType mp4() {
+                return "video/mp4";
+            }
+
             // </CODEGEN_COPY_TO_HEADER>
         }
     };