docs: add landing pages

[florentianayuwono]

Applicable spec:

Overview

Add landing pages for how-to and reference section.

Rationale

To aid user in navigating the documentations.

Juju Events Changes

Module Changes

Library Changes

Checklist

• The charm style guide was applied
• The contributing guide was applied
• The changes are compliant with ISD054 - Managing Charm Complexity
• The documentation for charmhub is updated
• The PR is tagged with appropriate label (urgent, trivial, senior-review-required, documentation)
• The docs/changelog.md is updated with user-relevant changes.

[github-actions]

license-eye has checked 77 files.

Valid	Invalid	Ignored	Fixed
27	2	48	0

Click to see the invalid file list

• docs/how-to/index.rst
• docs/reference/index.rst

Use this command to fix any missing license headers

```bash

docker run -it --rm -v $(pwd):/github/workspace apache/skywalking-eyes header fix

</details>

[Copilot]

Pull request overview

This PR adds landing page index files (index.rst) for the how-to and reference documentation sections of the aproxy charm. These landing pages provide structured navigation with categorized toctree directives, grouping existing documentation pages under themed subsections (e.g., "Basic operations", "Charm usage", "Architecture and deployments").

Changes:

• Added docs/how-to/index.rst with toctree sections for basic operations, update/refresh, and development guides.
• Added docs/reference/index.rst with toctree sections for charm usage and architecture/deployment references.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
docs/how-to/index.rst	New landing page for how-to guides, organizing configure, backup/restore, upgrade, and contribute pages into categorized sections.
docs/reference/index.rst	New landing page for reference documentation, organizing actions, configurations, integrations, and charm architecture pages into categorized sections.

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[erinecon]

Thanks so much!!

Note that you might want to add the landing pages into docs/index.md under the Contents section

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.

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