docs: add zed extension installation to USAGE.md and installation.md

[tzabbi]

Resolves #98

Checklist

• I have read the contribution guide.
• I have not used an AI coding assistant to create this PR.
• I have written all code in this PR myself OR I have marked all code I have not written myself (including modified code, e.g. copied from other places and then modified) with a comment indicating where it came from.
• I (and other contributors to this PR) have not looked at the Terraform source code while implementing this PR.

Go checklist

• I have run golangci-lint on my change and receive no errors relevant to my code.
• I have run existing tests to ensure my code doesn't break anything.
• I have added tests for all relevant use cases of my code, and those tests are passing.
• I have only exported functions, variables and structs that should be used from other packages.
• I have added meaningful comments to all exported functions, variables, and structs.

[Gogotchuri]

Thank you for your time. We love to see the community getting involved.
I have a few comments about the PR that need to be addressed before we can merge it.

Firstly, please only include changes that are relevant to the issue this PR solves. You should remove the reformatting changes. This will make reviewing much easier.

Also, please always link the issue you are addressing. In case such an issue doesn't exist, please create it first. In this case, I would mention it as "Relates to #48". I've gone ahead and made a sub-issue for Zed (#98) under #48 and edited your PR.

[tzabbi]

Thank you for your time. We love to see the community getting involved. I have a few comments about the PR that need to be addressed before we can merge it.

Firstly, please only include changes that are relevant to the issue this PR solves. You should remove the reformatting changes. This will make reviewing much easier.

Also, please always link the issue you are addressing. In case such an issue doesn't exist, please create it first. In this case, I would mention it as "Relates to #48". I've gone ahead and made a sub-issue for Zed (#98) under #48 and edited your PR.

Thank you for your help and your review! Hope I solved all issues.

[Gogotchuri]

Looks great!
Thank you for the changes.

[diofeher]

Looking good, thanks!

There's a small typo and then we can merge it :)