merge and diff and shared docs

[ahmedrowaihi]

feature 1 ( merge into any base branch )

currently APIDog only allows to merge forks into main, we wish it allows to support into different branch, in our case, we have

• main branch -> production deployed
• develop branch -> develop deployed
• [...] feature branches -> contains new API impl proposals to our backend team

and we wish to have the merge flow like this:

main <-- develop <-- [...] feature branches

feature 2 ( share docs diff )

when sharing docs for specific branch, allow showing diff to its base branch through the web interface