how to add a New chart type

[leesonwei]

Is your feature request related to a problem? Please describe.
https://github.com/airbnb/superset/pull/3013

Describe the solution you'd like
I want to add chart type use echart, then i follow https://github.com/airbnb/superset/pull/3013, but it did'nt work. some body can help me?

Describe alternatives you've considered
https://github.com/airbnb/superset/pull/3013

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[willbarrett]

Please fill out the full issue template so that the project maintainers can provide assistance.

[maltoze]

ref:
#8229
apache-superset/superset-ui-plugins#202

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[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions. For admin, please label this issue .pinned to prevent stale bot from closing the issue.