AnySceneImporter: recognize 3MF files.

A 3D printing format, Assimp can apparently import it.

doc/changelog.dox

@@ -488,6 +488,7 @@ See also:
     [mosra/magnum#529](https://github.com/mosra/magnum/pull/529))
 -   Recognizing KTX2 for (compressed) 1D/2D/3D and multi-level 1D/2D/3D images
     in @relativeref{Trade,AnyImageConverter}
+-   Recognizing 3MF files in @relativeref{Trade,AnySceneImporter}
 -   @ref Audio::AnyImporter "AnyAudioImporter",
     @relativeref{Trade,AnyImageImporter}, @relativeref{Trade,AnyImageConverter},
     @relativeref{Trade,AnySceneImporter}, @relativeref{Trade,AnySceneConverter}

src/MagnumPlugins/AnySceneImporter/AnySceneImporter.cpp

@@ -87,6 +87,8 @@ void AnySceneImporter::doOpenFile(const Containers::StringView filename) {
     if(normalizedExtension == ".3ds"_s ||
        normalizedExtension == ".ase"_s)
         plugin = "3dsImporter"_s;
+    else if(normalizedExtension == ".3mf"_s)
+        plugin = "3mfImporter"_s;
     else if(normalizedExtension == ".ac"_s)
         plugin = "Ac3dImporter"_s;
     else if(normalizedExtension == ".blend"_s)

src/MagnumPlugins/AnySceneImporter/AnySceneImporter.h

@@ -58,6 +58,8 @@ tries to open the file with it. Supported formats:
 
 -   3ds Max 3DS and ASE (`*.3ds`, `*.ase`), loaded with any plugin that
     provides `3dsImporter`
+-   3D Manufacturing Format (`*.3mf`), loaded with any plugin that provides
+    `3mfImporter`
 -   AC3D (`*.ac`), loaded with any plugin that provides `Ac3dImporter`
 -   Blender 3D (`*.blend`), loaded with any plugin that provides
     `BlenderImporter`

src/MagnumPlugins/AnySceneImporter/Test/AnySceneImporterTest.cpp

@@ -81,6 +81,7 @@ constexpr struct {
 } DetectData[]{
     {"Blender", "suzanne.blend", "BlenderImporter"},
     {"COLLADA", "xml.dae", "ColladaImporter"},
+    {"3MF", "print.3mf", "3mfImporter"},
     {"FBX", "autodesk.fbx", "FbxImporter"},
     {"glTF", "khronos.gltf", "GltfImporter"},
     {"OpenGEX", "eric.ogex", "OpenGexImporter"},