add edgeName to sankey

[ZNackasha]

Brief Information

this will allow the user to give a custom edge name on the edge of a Sankey

This pull request is in the type of:

• bug fixing
• new feature
• others

What does this PR do?

simply adds a variable to override the default edge name

Fixed issues

Details

Before: What was the problem?

After: How does it behave after the fixing?

Document Info

One of the following should be checked.

• This PR doesn't relate to document changes
• The document should be updated later
• The document changes have been made in apache/echarts-doc#xxx

Misc

ZRender Changes

• This PR depends on ZRender changes (ecomfe/zrender#xxx).

Related test cases or examples to use the new APIs

N.A.

Others

Merging options

• Please squash the commits into a single one when merging.

Other information

[echarts-bot]

Thanks for your contribution!
The community will review it ASAP. In the meanwhile, please checkout the coding standard and Wiki about How to make a pull request.

⚠️ MISSING DOCUMENT INFO: Please make sure one of the document options are checked in this PR's description. Search "Document Info" in the description of this PR. This should be done either by the author or the reviewers of the PR.

[echarts-bot]

Document changes are required in this PR. Please also make a PR to apache/echarts-doc for document changes and update the issue id in the PR description. When the doc PR is merged, the maintainers will remove the PR: awaiting doc label.

[Ovilia]

If you want to custom the tooltip, you can use series.tooltip.formatter like this demo. Otherwise, please explain in which cases this is necessary. Thanks!