Expand example on thumbnailing

[nathanl]

No description provided.

[kipcole9]

Thanks @nathanl, much appreciated.

[kipcole9]

I've pushed Image version 0.43.1 with the following changelog entry:

Bug Fixes

• Image.from_kino/2 and Image.from_kino!/2 now use the :file_ref field in the Kino input structure to identify the required image. This changed was added in Kino 0.11 which is therefore now a minimum version requirement. Thanks to @kevinschweikert for the PR. Closes from_kino/2: use file_ref instead of unused binary field from Kino.Input.read/1 #133.

• Improve the thumbnailing guide. Thanks to @nathanl for the PR. Closes Expand example on thumbnailing #132.

Thanks again for the contribution.