docs: add a preview page for reusing packages

[lengau]

Adds a preview page for how to reuse packages between builds.

Also prepares for the 5.11.0 release.

• Have you followed the guidelines for contributing?
• Have you signed the CLA?
• Have you successfully run make lint && make test?
• Have you added an entry to the changelog (docs/reference/changelog.rst)?

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[lengau]

There is no blank line here because otherwise the blank line would be included in the self-referential literalinclude.

[lengau]

Rendered: https://canonical-craft-application--929.com.readthedocs.build/en/929/how-to-guides/reuse-packages-between-builds/

[lengau]

Rendered: https://canonical-craft-application--929.com.readthedocs.build/en/929/reference/changelog/

[medubelko]

This isn't in line with what we want from a page of documentation.

I left it out of Craft Application because I didn't think the generic page would be of use to Craft Application readers. Do you want to include it instead?

[lengau]

I would definitely like it to be available in the docs so people can see what would look like in their app's docs (and make it more discoverable for app docs).

[lengau]

Marking as draft so we can discuss proper solutions here.