Add next point release of Spin

[tpmccallum]

Content must go through a pre-merge checklist.

Pre-Merge Content Checklist

This documentation has been checked to ensure that:

• [x] The title, template, and date are all set
• [x] Does this PR have a new menu item (anywhere in templates/*.hbs files) that points to a document .md that is set to publish in the future? If so please only publish the .md and .hbs changes in real-time (otherwise there will be a menu item pointing to a .md file that does not exist)
• [x] File does not use CRLF, but uses plain LF (hint: use cat -ve <filename> | grep $'\r' | wc -l and expect 0 as a result)
• [x] Has passed bart check

$ bart check content/spin/v2/cli-reference.md ✅ content/spin/v2/cli-reference.md $ bart check content/spin/v2/cache.md ✅ content/spin/v2/cache.md $ bart check content/spin/v2/http-outbound.md ✅ content/spin/v2/http-outbound.md $ bart check content/spin/v2/managing-templates.md ✅ content/spin/v2/managing-templates.md $ bart check content/spin/v2/manifest-reference.md ✅ content/spin/v2/manifest-reference.md $ bart check content/spin/v2/running-apps.md ✅ content/spin/v2/running-apps.md $ bart check content/spin/v2/writing-apps.md ✅ content/spin/v2/writing-apps.md

• [x] Has been manually tested by running in Spin/Bartholomew (hint: use PREVIEW_MODE=1 and run npm run styles to update styling)
• [x] Headings are using Title Case
• [x] Code blocks have the programming language set to properly highlight syntax and the proper copy directive
• [x] Have tested with npm run test and resolved all errors
• [x] Relates to an existing (potentially outdated) blog article? If so please add URL in blog to point to this content.

[vdice]

Pushed https://github.com/fermyon/developer/pull/1306/commits/2020ed845920fef86290789c4b93458ca0f254b8 since @tpmccallum may still be away during the forthcoming release.

cc @itowlson any other details to add to this PR? (Larger docs updates of course can/should be in separate PRs)

[itowlson]

We can also mention:

• The new registry option for component.source. This affects the manifest reference and, potentially, the writing applications page. It should be described as experimental at this stage, because the registry configuration stuff is not yet very friendly.
• spin up -f can point to a Wasm file instead of a manifest, e.g. spin up -f mymoduie.wasm. This could be mentioned on the "running applications" page. Although the uses are very limited outside test apps, because apps run this way have no access to files, storage, HTTP, etc.
• There's a convenience tweak to spin templates install where you can pass a GH repo id instead of the full URL e.g. spin templates install --git fermyon/spin. Not a big thing but could fit in an aside.

That's all I can see although my eyes did glaze over a bit trying to scan the commit list...!