Document adding SVGs as React components

[mareksuscak]

Preview

[holloway]

@mareksuscak One thing to document might be how the SVG component can accept props which are applied to the <svg> such as,

 <Logo className="icon" />  or  <Logo {...props} />

These props are essential for my use of SVG components because I have the same SVG with different dimensions and classNames.

Also when Jest snapshots are made of these SVG components in CRA2 it seems to just print their filenames.. there's no <svg>...</svg> tags, just a string of "icon.svg". Is that intentional? @Timer @gaearon

This means that the snapshots don't include these props, which (of course) means the snapshots are missing particular app states.

[gaearon]

@holloway Thanks for bringing it up. I think we discussed doing something like this and then forgot to fix it. Since 2.0 is not tagged at latest yet, I think it's acceptable to consider this a bugfix before final, and then insta-deprecate versions before the final one. We'll make a PR soon.

[Timer]

This was merged into next. Fixed via 9f7f2ab.

[gaearon]

oops thanks

[mareksuscak]

No worries, I was planning to update this PR later tonight but I'm glad you were able to cherry-pick the changes. Next time around, I'll make sure to allow edits from maintainers!