Support for Bitbucket server in Edit Link

[RecuencoJones]

Feature request

What problem does this feature solve?

From what I've seen in #1235, bitbucket cloud is now supported. However, bitbucket server uses a different format for the repository URL, it would be great to support this as well.

What does the proposed API look like?

In themeConfig, we could have something like this:

themeConfig: 
  docsRepo: bitbucket server # Match with a regex like /bitbucket.*server/i
  bitbucketServerRepo: https://my.bitbucket.server/projects/awesome/repos/documentation

How should this be implemented in your opinion?

I've tested so far the following changes PageEdit.vue:

https://github.com/RecuencoJones/vuepress/blob/c13b271bcd7d19049124ebcd2320c48585c45b45/packages/%40vuepress/theme-default/components/PageEdit.vue#L84-L94

Are you willing to work on this yourself?

Sure!