[excludeMimeTypes] Exclude model/obj and text/rust from content indexing
3D models, mimetype model/obj, are subtypes of plain/text and are content indexed by default. These files can be large and full of numbers.
Rust source seems be to content indexed by default, by comparison C and C++ source is excluded on the basis of their mime types.
Excluding these by mimetype means that Baloo will continue to index the filenames but not the content
(The model/obj mimetype seems to be a recent addtion to the freedesktop.org.xml list, it may not be present in LTS distros)