Update DefaultPortModel.ts

[lancety]

this is about fixing a type error when creating custom port model; when making custom port widget with custom styled link, I need to make a custom port model, which need a custom type in constructor's options object, but options.type is missing in the DefaultPortModel constructor props type. So I added it in.

Checklist

• [ ] The code has been run through pretty yarn run pretty
• [ ] The tests pass on CircleCI
• [ ] You have referenced the issue(s) or other PR(s) this fixes/relates-to
• [ ] The PR Template has been filled out (see below)
• [ ] Had a beer/coffee because you are awesome

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[dylanvorster]

The thing is though, you should not extend from Default if you want to make your own models, thats why type is hardcoded to default.