Open room member avatar in a media viewer (#1911)

* Open room member avatar in viewer.

The `MediaViewer` was extracted to its own library module.

* Update screenshots

* Restore KSP processor in `:libraries:mediaviewer:api`, this should generate Showkase components again.

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Co-authored-by: ElementBot <benoitm+elementbot@element.io>

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/media/RustMediaLoader.kt

@@ -82,7 +82,7 @@ class RustMediaLoader(
                     val mediaFile = innerClient.getMediaFile(
                         mediaSource = mediaSource,
                         body = body,
-                        mimeType = mimeType ?: MimeTypes.OctetStream,
+                        mimeType = mimeType?.takeIf { MimeTypes.hasSubtype(it) } ?: MimeTypes.OctetStream,
                         useCache = useCache,
                         tempDir = cacheDirectory.path,
                     )