Add a badge for libdicom Conan package to README.md

[valgur]

Entirely optional, mostly just letting you know that libdicom is now also available as a Conan package.

[jcupitt]

That's very cool! Thank you @valgur

Do you plan to package openslide4 as well? libvips 8.15 (just out) has openslide4 support, so it'd be great to see them all move together.

[valgur]

@jcupitt Was not planning to, but I gave it a shot: conan-io/conan-center-index#21138

Will add it to libvips as well once it gets merged.

[jcupitt]

That's great! Thank you.

libdicom just gets the tiles from the file, you need quite a bit more code (eg. openslide) to assemble them into pyramids and decode to RGB pixels.