Update snap.md

Author: chennes

technical/snap.md

@@ -22,9 +22,15 @@ if the snap-building logs contain errors about being unable to locate neon, chec
 https://snapcraft.io/docs/kde-neon-extension and update it everywhere it appears in the snapcraft.yaml file.
 
 Snaps are built based on specific "cores" -- the base operating system whose libraries they use. From time to time
-we have to update to a new core. The current builds use "core20", or Ubuntu 20.04 LTS. Updating the core will likely
+we have to update to a new core. The current builds use "core22", or Ubuntu 22.04 LTS. Updating the core will likely
 require updating many of the other version numbers in the snap YAML file.
 
+## Dependencies
+
+Several of FreeCAD's dependencies take a long time to build and seldomly change: the two largest culprits here are
+OCCT and GMSH. These two packages have been split into their own "unlisted" snap, called freecad-deps-core22. To
+update the versions of those libraries, that snap is the one that must be updated, ratheer than freecad-snap itself.
+
 ## Important links
 
   * https://snapcraft.io/freecad