Update `pnpm` to `v9` & improve CI

[xeho91]

Following the request: https://github.com/storybookjs/addon-svelte-csf/pull/179#pullrequestreview-2053802933

Additional context

• Added .nvmrc (I've used version that matched the previous CI workflows setup - 20), so my machine can automatically set up the right version.
• Upgraded CI workflows actions, and reduced one action - pnpm/action-setup - in favor of corepack

📦 Published PR as canary version: 4.1.3--canary.180.930cbf4.0

:sparkles: Test out this PR locally via: ```bash npm install @storybook/addon-svelte-csf@4.1.3--canary.180.930cbf4.0 # or yarn add @storybook/addon-svelte-csf@4.1.3--canary.180.930cbf4.0 ```

[xeho91]

@JReinhold I'm puzzled how the Chromatic workflow was able to run successfully before, without the building step 🤔 👀

[shilman]

:rocket: PR was released in v4.1.3 :rocket: