Document learnings about JPEGs

Author: adamtheturtle

CONTRIBUTING.rst

@@ -183,6 +183,9 @@ A target with the name ``\uffff`` gets stuck in processing.
 The documentation page `How To Perform an Image Recognition Query <https://library.vuforia.com/articles/Solution/How-To-Perform-an-Image-Recognition-Query>`__ states that "The API accepts requests with unknown data fields, and ignore the unknown fields.".
 This is not the case.
 
+The documentation page `How To Perform an Image Recognition Query <https://library.vuforia.com/articles/Solution/How-To-Perform-an-Image-Recognition-Query>`__ states "Maximum image size: 2.1 MPixel. 512 KiB for JPEG, 2MiB for PNG".
+However, JPEG images up to 2MiB are accepted.
+
 Performing a release
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