Tweak gitignore;

- Machine-specific excludes do not belong in lovr's gitignore.
  They should be configured using .git/info/exclude or globally.
- Preferential excludes should use .git/info/exclude (e.g.
  plugins, in-tree lua files).
- This restricts gitignore to build-system-generated artifacts.
  Honestly I'd like to remove these too, but need to monitor.

.gitignore

@@ -1,13 +1,5 @@
-.DS_Store
-.vs
 .tup
 .obj
 bin
 build*
-plugins
 *.*.h
-*.lua
-*.config
-Activity*.java
-AndroidManifest*.xml
-deps/OpenXR-Oculus

Tupfile.lua

@@ -452,7 +452,7 @@ if target == 'android' then
     config.headsets.pico and 'src/resources/Activity_pico.java' or
     config.headsets.openxr and 'src/resources/Activity_openxr.java'
 
-  java = 'src/resources/Activity.java'
+  java = 'bin/Activity.java'
   class = 'org/lovr/app/Activity.class'
   binclass = 'bin/' .. class
   jar = 'bin/lovr.jar'