docs: Pin @rspack/core to 1.5.8 (#778)

Pins `@rspack/core` to version 1.5.8 in the website folder to ensure
consistent builds and avoid potential breaking changes from patch
updates.

## Changes

- Added `overrides` field to `website/package.json` specifying
`@rspack/core: "1.5.8"`
- Regenerated `website/package-lock.json` to reflect the pinned version

The override forces all transitive dependencies (primarily
`@docusaurus/faster`) to use exactly version 1.5.8 of `@rspack/core`.

> [!WARNING]
>
> <details>
> <summary>Firewall rules blocked me from connecting to one or more
addresses (expand for details)</summary>
>
> #### I tried to connect to the following addresses, but was blocked by
firewall rules:
>
> - `googlechromelabs.github.io`
>   - Triggering command: `node install.mjs` (dns block)
> -
`https://storage.googleapis.com/chrome-for-testing-public/141.0.7390.54/linux64/chrome-linux64.zip`
>   - Triggering command: `node install.mjs` (http block)
>
> If you need me to access, download, or install something from one of
these locations, you can either:
>
> - Configure [Actions setup
steps](https://gh.io/copilot/actions-setup-steps) to set up my
environment, which run before the firewall is enabled
> - Add the appropriate URLs or hosts to the custom allowlist in this
repository's [Copilot coding agent
settings](https://github.com/apify/apify-client-js/settings/copilot/coding_agent)
(admins only)
>
> </details>

<!-- START COPILOT CODING AGENT SUFFIX -->



<details>

<summary>Original prompt</summary>

> in website folder, pin `@rspack/core` to 1.5.8 via npm overrides and
regenerate lockfile


</details>



<!-- START COPILOT CODING AGENT TIPS -->
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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: B4nan <615580+B4nan@users.noreply.github.com>

Author: Copilot

website/package-lock.json

@@ -15,6 +15,9 @@
         "lint:md": "cd .. && markdownlint 'website/**/*.md' 'docs/**/*.md' && cd website",
         "lint:md:fix": "cd .. && markdownlint 'website/**/*.md' 'docs/**/*.md' --fix && cd website"
     },
+    "overrides": {
+        "@rspack/core": "1.5.8"
+    },
     "devDependencies": {
         "@apify/tsconfig": "^0.1.0",
         "@types/react": "^19.0.0",