Put Image component into Psammead

[sareh]

Is your feature request related to a problem? Please describe.
Create an Image component in Psammead, looking at the one in Simorgh:

Corresponding 'pull from Psammead' issue in Simorgh: bbc/simorgh#1077.

Note: update the README.md to include standard sections: https://github.com/BBC-News/psammead/tree/latest/packages/components/psammead-paragraph

Describe the solution you'd like
A PR in Psammead, which adds an Image component.

Describe alternatives you've considered
N/A

Testing notes
Check to make sure component displays (with styling) as expected in Storybook.

Dev insight: Unit tests (if any) will be transferred from Simorgh.

Additional context
N/A

• Initially labelled with "Refinement needed"

[ChrisBAshton]

Blocked on bbc/simorgh#929

[ChrisBAshton]

bbc/simorgh#929 is proving more difficult than anticipated.

We can pick up #203 in the meantime, and then port across the AmpImg PR to Psammead once we've nailed it in Simorgh.