This is required to keep add-on logos working for 3.4.x, because with
the introduction of SVG logo support and the conversion of some logos,
3.4.x would not be able to display SVG logos.
For the docs, it is also really helpful to link to the docs matching the
version, because due to the number of breaking changes for openHAB 4.0
there are larger difference in parts of the docs. Linking the wrong
could cause confusion.
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Signed-off-by: Florian Hotze <florianh_dev@icloud.com>