Add readme to uk-nowcasting

[peterdudfield]

Detailed Description

Would be good to add a read me to the development and production

Context

• good to have good docs

Possible Implementation

• say what it is, what componnents are in it
• add a diagram of both things, for example -
• perhaps we update one from here - https://docs.google.com/presentation/d/1LHZZ7AjfJFGmi3GYiVufI7BGETllI5ug3LO7tvaccdQ/edit#slide=id.g1502fe07f55_0_0
• or create a new one

[devsjc]

https://github.com/openclimatefix/ocf-infrastructure/pull/354

Architecture diagram is under construction...

[peterdudfield]

Ill close this for now, as there is faiurly good readme in there now