Re-add image/avif in MediaType.

(And this time, include a `@since` tag :))

We'd originally added this in cl/723988216 but then withdrew it in cl/728267849 so that we could release a [module-system-friendly](#2970) version of Guava as a _patch_ release, rather than as a _minor_ release.

RELNOTES=`net`: Added `image/avif` to `MediaType`.
PiperOrigin-RevId: 728268046

Author: cpovirk

android/guava/src/com/google/common/net/MediaType.java

@@ -252,6 +252,13 @@ private static MediaType addKnownType(MediaType mediaType) {
   public static final MediaType SVG_UTF_8 = createConstantUtf8(IMAGE_TYPE, "svg+xml");
   public static final MediaType TIFF = createConstant(IMAGE_TYPE, "tiff");
 
+  /**
+   * <a href="https://en.wikipedia.org/wiki/AVIF">AVIF image format</a>.
+   *
+   * @since NEXT
+   */
+  public static final MediaType AVIF = createConstant(IMAGE_TYPE, "avif");
+
   /**
    * <a href="https://en.wikipedia.org/wiki/WebP">WebP image format</a>.
    *

guava/src/com/google/common/net/MediaType.java

@@ -252,6 +252,13 @@ private static MediaType addKnownType(MediaType mediaType) {
   public static final MediaType SVG_UTF_8 = createConstantUtf8(IMAGE_TYPE, "svg+xml");
   public static final MediaType TIFF = createConstant(IMAGE_TYPE, "tiff");
 
+  /**
+   * <a href="https://en.wikipedia.org/wiki/AVIF">AVIF image format</a>.
+   *
+   * @since NEXT
+   */
+  public static final MediaType AVIF = createConstant(IMAGE_TYPE, "avif");
+
   /**
    * <a href="https://en.wikipedia.org/wiki/WebP">WebP image format</a>.
    *