Fix oversized inline SVGs when css is disabled

[andymantell]

Description

Add width, height, stroke and fill attributes to inline SVGs in order that they render at appropriate sizes when viewed with disabled/broken/missing CSS

Fixes #747

Checklist

• Tested against our testing policy (Resolution, Browser & Accessibility)
• Follows our coding standards and style guide
• CHANGELOG entry

[chrimesdev]

This looks good to me, we just need to update the HTML markup in the individual component README files eg. https://github.com/nhsuk/nhsuk-frontend/blob/master/packages/components/action-link/README.md

We're planning on moving the HTML markup out of the README and just have the single source of HTML/Nunjucks truth on the NHS digital service manual - but for now we best just update it in there too.

Also I think we might need to update the SVG asset files incase anyone uses them for includes found in the packages/assets/icons folder eg. https://github.com/nhsuk/nhsuk-frontend/blob/master/packages/assets/icons/icon-arrow-left.svg?short_path=e101404

[andymantell]

@chrimesdev For the heights/widths inside the SVG files themselves - some of the SVGs are used in multiple places with different dimensions, so it's not possible for me to set the "correct" dimensions in each file for every case. I have therefore defaulted the SVG files to 34px x 34px which is the same as the default $nhsuk-icon-size from the SCSS. If people are including them in this manner, this should still be sufficient to tidy up the default output.

[andymantell]

@chrimesdev I have addressed your comments and this one is ready for review again. Cheers!

[chrimesdev]

Looks good thanks @andymantell