Document flag creation practices

[emily-noble]

Many pride flags have some issues with image quality. Some examples:

• Non-svg format (requiring manually creating an svg version)
• Inconsistent stripe widths (when it's only a pixel or two difference, it's likely the author intended equal widths)
• Shape distortion (I've seen variations on the intersex pride flag where the circle is stretched to an oval)
• Composite flags (ex: Trans Intersex flag) using different colors than their separate parts

Document in both the README and in a separate page on the website (perhaps an "FAQ" page?) how these decisions are handled and addressed. Determine if (and how) to indicate when a flag on the website has been modified in colors, layout, etc from the original.

Additionally document things that should not be changed when adding or updating a new flag image.