docs: add plugins documentation

[rishabh998186]

I noticed users have trouble finding information about plugins and their versions since everything's mixed in the releases page. This PR adds a dedicated plugins section to make that easier.

Right now if someone wants to:

• See what plugins are available
• Find docs for a specific plugin
• Check plugin versions

They have to dig through the releases page or search around the docs. Not ideal.

so i make some changes :

1. Added /docs-dev/user-guide/plugins/ section

• Overview page that lists all 8 plugins
• Detailed pages for Kubernetes, Terraform, and Cloud Run
• Each page includes:
  • What the plugin does
  • How to configure it
  • Code examples
  • Available deployment stages

2. Updated README

Added a quick reference table after the "Why PipeCD?" section so people can find plugins immediately.

Kubernetes, Terraform, and Cloud Run are the most commonly used. If this approach works well, I can add pages for the remaining plugins (Analysis, Script Run, Wait, Wait Approval).

This structure sets us up for:

• Automated version tracking (when plugins get independent releases)
• Compatibility matrices
• Per-plugin changelogs

Let me know if you'd like any adjustments or if I should add the remaining plugin pages in this PR instead!

closes #6265

[rishabh998186]

- Enhance plugins documentation with current version table

- Fix YAML formatting in all plugin documentation files  

[eeshaanSA]

@rishabh998186 Thanks for this.

Question: How much AI have you used in this PR?

Nothing against it, completely okay to use it, just asking so that I can review your changes better.

[rishabh998186]

@eeshaanSA I used AI as a drafting tool and to help with clarity, but all the technical content is based on PipeCD's actual codebase and documentation.

[eeshaanSA]

You are going on the right track, @rishabh998186. We need documentation for our plugins, and yes, your structure is right, the pages you have created are right. And yes, this is going to be very helpful.

But, none of your code snippets demonstrate how the new plugin architecture works. The piped config file and the application config files are way off. This is likely because of the use of AI (the feature is relatively new, so AI might not have a lot of data on it).

I would suggest you to join our Slack channel, go through the concept of pluggable-PipeCD, practice some v1 deployments first, and learn how the plugin architecture works. Happy to provide you with all the resources and help you out. 😃

[rishabh998186]

Thank you so much for the detailed feedback, @eeshaanSA! i realize that I relied too much on AI for the configuration examples, and it clearly doesn't have accurate information about the new plugin architecture. I apologize for the inaccurate code snippets.

Once I have a better understanding of how the plugin architecture actually works, I'll update the PR with accurate examples.Thanks again for the guidance .

[eeshaanSA]

Hey @rishabh998186,

How is it going? I noticed that you are trying to push some commits. How is it going with this issue so far? Do you need any help?

[rishabh998186]

@eeshaanSA
Sorry I went quiet - my laptop broke and I just fixed it. I'm back now and ready to work on this again. if i get stuck or need help, I'll ask. Thanks for checking in.

[rishabh998186]

@eeshaanSA Hey, I've made some changes and added the remaining plugin files. Do they look good or is there anything that needs to be changed?

[rishabh998186]

hey @eeshaanSA

could you take a look at these docs and give your feedback on them ?