Simple documentation fix: add link to Developer Hub

On https://developer.companieshouse.gov.uk/api/docs/index/gettingStarted/apikey_authorisation.html, the words ‘Companies House Developer Hub’ should be a link to ‘https://developer.companieshouse.gov.uk/developer/applications

The only way I found the real link was to visit this forum.

I agree that this could be clearer, but something more along the lines of:

“To obtain an API key, go to ‘Your applications’ and register a new application”

With ‘Your applications’ linking to the relevant page.