This adds an extremely simple Mandala page (for #24) with a single circle Mandala comprised of several eyes. The symbol style is configurable, but parameters for the actual Mandala are not (yet).
Doing this also involved factoring out a `<SvgTransforms>` component, which makes setting up SVG transforms a bit easier.
Also moved `getSymbol` of `creature-page.tsx` and into `svg-vocabulary.tsx`, with the new name `getSvgSymbol`.
This fixes a bunch of bugs in our attachment-related code, and in so doing refactors things to make more sense, adds more tests, and also adds documentation.
Atul Varma