A fix to the formatting of the documentation for endShape's instancing example

[RandomGamingDev]

Resolves an issue with the formatting of the instancing example for endShape()

Changes:

This decreases the size of the canvas so that the example code can be formatted properly, and centers the squares used in the example to make it look nicer.

Screenshots of the change:

Here's what it currently looks like (400x400 canvas is used for the example):

Here's how the new 100x100 canvas which will fix the formatting:

PR Checklist

• npm run lint passes
• Inline documentation is included / updated
• Unit tests are included / updated

[davepagurek]

Thanks @RandomGamingDev!