It's White, not Neutral, and it's probably (almost certainly, really) a switch loop. (So it's Hot.)
Per current code it should be remarked with red (my preference) or black or any other "hot color" at the ends, but it's common to encounter switch loops that were not so marked, either from before the code change or from workers who ignored the code change.
Additional pictures confirm it's a switch loop. Save some future pain and pull/twist/poke a pin in the holes of that switch to remove the wires from the "backstab holes" that go bad, and put them on the side screws that don't go bad.
Cut a short piece of white wire and connect it to the two white wires (that are Neutral) on the one screw of the lamp fixture with a wirenut or other suitable connector, and connect the free end of it to the screw on the fixture - it is indeed incorrect for that type of screw to have more than one wire. If you are planning to add an outlet, go ahead and add the neutral from that outlet to the bundle.
Since this appears to be an open/accessible garage situation, one option you might want to consider would be to go ahead and replace the 14/2 to the switch with a 14/3, thus bringing that switch box up to current code. You are not required to upgrade "grandfathered" work that was acceptable when installed unless making major revisions, but if it's easy to do, you might at least consider doing that. You could re-use the 14/2 for your new outlet.