Fix remaining warnings and treat as errors for build so CIs detect them

[CAM-Gerlach]

Presently, there are a couple remaining build warnings:

6:41:52 PM [vite-plugin-svelte] /home/runner/work/spyder-website/spyder-website/node_modules/svelte-youtube-embed/Youtube.svelte:44:4 A11y: <div> with click, keypress handlers must have an ARIA role
42:       <Image {id} {title} {altThumb} {play} />
43:     {/if}
44:     <div class="b__overlay" on:click={() => (play = true)} on:keypress={() => (play = true)} />
        ^
45:     <div class="v__title"><h3>{title}</h3></div>
46:   {/if}
✓ 200 modules transformed.
rendering chunks...
[plugin:vite:reporter] [plugin vite:reporter] 
(!) /home/runner/work/spyder-website/spyder-website/src/lib/components/VideoPlayer.svelte is dynamically imported by /home/runner/work/spyder-website/spyder-website/src/lib/components/Tabs.svelte but also statically imported by /home/runner/work/spyder-website/spyder-website/src/lib/blocks/ContentBlock.svelte, dynamic import will not move module into another chunk.

Presumably, these should be fixed (or suppressed, if they are false positives).

Additionally, there is no indication in CI of any newly introduced warnings (forcing authors and reviewers to manually manually click through to the relevant part of the logs and trawl through them looking for them, which takes valuable time and is unlikely to happen in practice). To fix this, the relevant build flags/options should be set such that warnings cause the build to exit non-zero (i.e. report as successful), as we have on our other docs and web sites.

It should be configured so that the build does not simply halt on the first warning, but instead completes (showing all warnings and any critical errors) and then exits non-zero, which may require an extra option. Ideally, this would be set so that the GitHub Actions run fails but the Netlify build succeeds, so it does not block viewing the preview, though that may require some action on my side as well (I'm not sure if we've routinely done this on our various other sites).