fix: edit page from Bitbucket

[daltondiaz]

The edit page from Bitbucket (is used a GET request with some parameters) is different from Gitbhub ( add /edit ). For example:

Bitbucket: https://bitbucket.org/myrepo/bitbucket-vuepress/src/master/docs/README.md?mode=edit&spa=0&at=master (This not exist)

Github: https://github.com/vuejs/vuepress/edit/master/docs/README.md

For test I create a repository in Bitbucket with vuePress and worked!

Summary

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Docs
• Build-related changes
• Other, please describe:

If changing the UI of default theme, please provide the before/after screenshot:

Does this PR introduce a breaking change? (check one)

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)

You have tested in the following browsers: (Providing a detailed version will be better.)

• Chrome
• Firefox
• Safari
• Edge
• IE

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature
• Related documents have been updated
• Related tests have been updated

To avoid wasting your time, it's best to open a feature request issue first and wait for approval before working on it.

Other information:

[ulivz]

LGTM