Improved rendering (And documentation) for 2d and 3d Lines

[jgrey8504]

The Problem:

Currently, it is difficult to utilize basic lines in your bevy project. The best 2 options are to use bevy polyline, or to import the shader assets from bevy main into your project, neither of which are very obvious or clear to beginners, and it is not very clean or straightforward to have to either import new dependencies or shaders into your project.

Additionally, they only work with 3d, being incompatible with 2d cameras. They also are incredibly difficult and unintuitive to work with, (With Bevy main's line shader) it is a challenge to even be able to move the lines during run time, and it has a lot of overhead, which makes it extremely difficult to even get to use without copying and pasting from this one example.

Solution:

It would be immensely helpful to have functions built-in that allow spawning bundles for lines in both 3d and 2d, which work 'out of the box' without needing to import/copy+paste a bunch of things, with documentation to make it more intuitive to use, implemented similarly to the shapes geometry bundles, which you can easily spawn with a spawn_bundle (The attributes all labeled), and then very simply edit on the fly with just a simple mutable query, as opposed to the lines right now, which... I'm not quite sure how it is intended to be edited??.. uh.. or the bevy polylines which require all sorts of handles and assets, which you get_mut another handle then unwrap and it's a whole difficult process.

Thanks in advance!