Add kra and ora imageio plugins (read-only)

kra is the native format for Krita and ora the interchange format
for krita, gimp and mypaint (it's also mypaint's native format).
Both formats are simply zip containers with an embedded png.

REVIEW:126675

autotests/CMakeLists.txt

@@ -61,6 +61,14 @@ kimageformats_read_tests(
     rgb
     tga
 )
+
+if (KF5Archive_FOUND)
+    kimageformats_read_tests(
+        kra
+        ora
+    )
+endif()
+
 # Allow some fuzziness when reading this formats, to allow for
 # rounding errors (eg: in alpha blending).
 kimageformats_read_tests(FUZZ 1