main-branch gitignore changes

I did *not* include renderer/lib - AFAICT this hasn't been useful
since renderer was added to the dash repo, because you can't npm i
a subdirectory of a repo from a gh link. So lib is only useful
as published on npm, and there it *is* included.

Author: alexcjohnson

.gitignore

@@ -49,7 +49,6 @@ downloads/
 eggs/
 .eggs/
 lib/
-!dash-renderer/lib
 lib64/
 parts/
 sdist/
@@ -81,3 +80,7 @@ VERSION.txt
 
 # vim
 *.swp
+
+# main-branch artifacts to explicitly include
+!dash/dash-renderer/build
+!dash/deps