chore: update github actions

[djm158]

Description

Updated to the following actions versions:

• checkout@v4
• setup-node@v4

Replaced yarn cache setup that previously used actions/cache with actions/setup-node

Removed OS matrix, set runner to ubuntu-latest and node-version to 18.

Additionally, updated README with NearForm banner/badges.

Type of Change

• Adding or updating CI (Actions)

[changeset-bot]

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Latest commit: 984fe53

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