Add documentation for IntelliSense for Zed

[SimonSimCity]

Description

I'm using Zed as editor and I wanted to provide introductions for enabling IntelliSense in Zed also to other people starting to use Zed.

I didn't quite follow the convention for naming commits. To the one merging: please squash the commit and add a proper commit message.

Additional context

I got the configuration from zed-industries/zed#5830 (comment) and tested it myself and found it working. It's very similar to the one for vscode.

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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

• Read the Contributing Guidelines.
• Follow the Style Guide.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).

[vercel]

@SimonSimCity is attempting to deploy a commit to the Joe Bell OSS Team on Vercel.

A member of the Team first needs to authorize it.

[joe-bell]

Thanks for this @SimonSimCity! I've already added this in the beta docs, but I don't see the harm in adding it here too