Update "Share chart" dialog wording

[emilykl]

• Update "Share chart" dialog with more informative wording
  • Add hyperlink to Plotly Cloud
• Update button tooltip to add an ellipsis ("Share chart...")
• Update and add Jasmine tests to cover dialog code

Codepen demo: https://codepen.io/emilykl-code/pen/PwWKqej

Dialog

Button tooltip

[red-patience]

LGTM!

[ndrezn]

Should this be sentence case? @red-patience

[red-patience]

Should this be sentence case? @red-patience

If this sets a new precedent then I would recommend sentence case but if not, then consistency with what exists already.

[emilykl]

Should this be sentence case? @red-patience

Which part?

[ndrezn]

"Share chart" instead of current "Share Chart"

[emilykl]

@red-patience @ndrezn I don't feel strongly either way, and there's not much precedent in plotly.js itself, so I've lowercased the word "chart" both in the button tooltip and the dialog title.