Fix #2189 broken documentation links and wrong default directory name

[jakubmakielkowski]

Description

1. Documentation links might be mismatched Links in this repository navigate to devtools-next documentation page instead of devtools-v6. These websites have different /docs structure, resulting in 404 errors. Changing devtools.vuejs.org to devtools-v6.vuejs.org resolves the problem.

Correct links:

devtools-v6 docs: https://devtools-v6.vuejs.org devtools-next docs: https://devtools.vuejs.org

List of correct fixed links:

• https://devtools-v6.vuejs.org/
• https://devtools-v6.vuejs.org/guide/faq.html#the-vue-devtools-don-t-show-up
• https://devtools-v6.vuejs.org/guide/devtools-perf.html
• https://devtools-v6.vuejs.org/guide/faq.html
• https://devtools-v6.vuejs.org/guide/open-in-editor.html
• https://devtools-v6.vuejs.org/plugin/plugins-guide.html
• https://devtools-v6.vuejs.org/guide/installation.html
• https://devtools-v6.vuejs.org/guide/installation.html#legacy
• https://devtools-v6.vuejs.org/guide/contributing.html
• https://devtools-v6.vuejs.org/guide/contributing.html#pull-request-guidelines

2. Installation default directory name The default directory name when cloning the repo is devtools-v6 instead of devtools. packages\docs\src\guide\contributing.md

Additional context

---

What is the purpose of this pull request?

• [X] Bug fix
• [ ] New Feature
• [ ] Documentation update
• [ ] Other

Before submitting the PR, please make sure you do the following

• [X] Read the Contributing Guidelines.
• [X] Read the Pull Request Guidelines and follow the Commit Convention.
• [X] Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• [X] Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).

[jakubmakielkowski]

Resolves https://github.com/vuejs/devtools-v6/issues/2188