add new linter to upport repairing import grouping/ordering

[daixiang0]

Is your feature request related to a problem? Please describe.

See this discuss.

Describe the solution you'd like

Introduce gci as a new linter.

Additional context

Golang community has little inseret about imporing it, but it would be useful for both contributors and maintainers.

Now gci implement basic functions，i think add it as new linter would be very cool.

WDYT? @golangci/team

[SVilgelm]

Looks like the gci is a very useful linter, but

1. it should support go/analysis interface
2. the gci implementation contains only main package that prevents the other applications to import that tool

[daixiang0]

I will refactor it.

[daixiang0]

Done.