Fix Sparkle framework to use symlinks

Currently, the embedded Sparkle.framework does not use symlinks as it should. Instead, it duplicates the executable and other files multiple times. To see how it should be, compare with an original Sparkle.framework

Start by locating the embedded Sparkle.framework in the MacDown project and compare its structure with an original Sparkle.framework, as requested. Verify that the executable and other repeated files are represented with symlinks rather than duplicated; the work is done when the embedded framework matches that structure.

Written by the indexing model from the issue text.