Adding second footprint for 3V3 voltage regulator (#98)

The voltage regulator that was originally used isn't available at the moment. To provide more options, a second footprint was added to the PCB for an alternative regulator that has a different pinout. Important to note that only one regulator should be used.

Also, adjusted .gitignore for Mac files and KiCad auto-generated backups.

.gitignore

@@ -9,6 +9,7 @@
 fp-info-cache
 _autosave*.kicad_pcb
 *.kicad_prl
+electronics/*/*backups
 
 # Proprietary 3d model (for KiCAD)
 **/proprietary/*.stp
@@ -20,6 +21,9 @@ _autosave*.kicad_pcb
 # General build outputs
 build/
 
+# Apple/Macintosh
+.DS_Store
+
 # VSCode
 .vscode/*
 !.vscode/settings.json

electronics/view_base/view_base.kicad_pro

@@ -443,4 +443,4 @@
     "COMMIT_HASH": "deadbeef",
     "RELEASE_VERSION": "v#.#"
   }
-}
+}