added missing installation instructions

[surrealroad]

#7083

Issue

#7083

Description

Adds the instructions for installation for npm and yarn, which were missing

Testing

Documentation only change

Additional context

The framework home page links to this readme but the instructions were missing.

Checklist

• If you wrote E2E tests, are they resilient to concurrent I/O?
• If adding new public functions, did you add the @public tag and enable doc generation on the package?

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[trivikr]

The install example is on the list item 2 already. It's on line 79 of this version of the PR.

Do you want to add npm install there instead?

[surrealroad]

No, because I think there are two different purposes being served:

1. I just want to know how to install
2. I want to see more of an end-to-end example of how to get started

For 1 (which was my particular use case, and why I opened the PR) I don't know that I want to scan through the end-to-end example to find the one command I'm looking for.