Add "top left" & "top center" side options to legend title

[28raining]

To help solve #6668

Added more options to 'side' inside layout -> legend so that when legend is in horizontal orientation the title can be aligned [left, center, right]

One strange thing is that 'top center' and 'top right' work as expected, but to get 'top left' you need to use 'top'.
Because 'top left' is already being used to move the title to the outside-left-side of the legend.
IMO it's a weird behavior but it's been purposely coded, so I didn't touch it

[28raining]

mapbox is failing because this domain is down / gone

https://img.nj.gov

which is used in this baseline:
plotly.js/test/image/mocks/mapbox_layers.json

[archmoj]

Thanks for the PR.
FYI - The baseline tests were now passed.

[archmoj]

Great PR.
1 - Let's modify one of the mocks so that it has the top right option.
2 - What does happen if you have these options on a legend with the orientation set to v?

[28raining]

Thank you.
1 - Top right test added to existing mock. This highlighted need to account for right-side-border
2 - Added top center to a vertical legend mock. Top, top center and top right do work with vertical too, I believe it's orientation agnostic.

[archmoj]

Nicely done.
Thanks very much for the PR.
💃