Custom input CSS infiltrates into SVG outputs

[fdoflorenzano]

Describe the bug
When custom inputs are used in mechanic project, their CSS also infiltrates into a design function's iframe because of dependencies, and therefore SVG outputs also get injected their CSS. In some cases, that CSS isn't automatically removed. I specifically had this with the ui-components CSS definitions, and had SVG outputs that triple in weight because of these.

A specific setting is introduced (ignoreStyles) in #128 to patch this, but that also ignores the design function's CSS. So currently having only the design function's CSS but not any from custom inputs is a bit tricky.

Expected behavior
SVG outputs not to contain custom input's CSS automatically.

Desktop (please complete the following information):

• OS: macOS Monterrey 12.3.1
• Browser: Firefox 99.0.1