Improve new repository documentation setup instructions

[petercrocker]

This PR improves the documentation for setting up new repositories to sync their docs to the infrahub-docs aggregation site, and adds automation tooling to simplify the process.

Changes

Improved README documentation:

• Rewrote the "How to Setup a New Repo" section with clearer, step-by-step instructions
• Added prerequisites section
• Split instructions into three parts: source repo setup, infrahub-docs setup, and final steps
• Added detailed file structure showing exactly what needs to be copied
• Added specific configuration guidance for each file that needs modification
• Added troubleshooting section for common issues
• Documented the proper ordering of PR merges (infrahub-docs first)

Added setup automation script (scripts/setup-docs-repo.py):

• Automates copying template files to new source repositories
• Applies placeholder substitutions for project name, display name, and sidebar names
• Creates placeholder files and sidebar config in infrahub-docs
• Generates docusaurus plugin configuration snippets to copy/paste
• Supports setting up source repo only, infrahub-docs only, or both at once

Added bundled templates (scripts/templates/):

• Complete Docusaurus site template with placeholder substitutions
• Linting configuration (Vale, markdownlint, yamllint)
• GitHub Actions workflows (sync-docs.yml, CI file filters)
• No external repository dependency required

Usage

# Setup both repos at once
python scripts/setup-docs-repo.py \
  --source-repo /path/to/my-new-project \
  --infrahub-docs-repo /path/to/infrahub-docs \
  --display-name "My New Project"

# Setup source repo only
python scripts/setup-docs-repo.py \
  --source-repo /path/to/my-new-project \
  --display-name "My New Project"

# Setup infrahub-docs only
python scripts/setup-docs-repo.py \
  --infrahub-docs-repo /path/to/infrahub-docs \
  --project-name my-new-project \
  --display-name "My New Project"

Template placeholders

The bundled templates use these placeholders that get substituted automatically:

• {{PROJECT_NAME}} - e.g., my-new-project
• {{PROJECT_PASCAL}} - e.g., MyNewProject (for sidebar names)
• {{PROJECT_DISPLAY_NAME}} - e.g., My New Project (for UI labels)

[cloudflare-workers-and-pages]

Deploying infrahub-docs with    Cloudflare Pages

Latest commit:	8ddd6d0
Status:	✅  Deploy successful!
Preview URL:	https://1cb4e0e9.infrahub-docs.pages.dev
Branch Preview URL:	https://pmc-20251220-new-repo-docs.infrahub-docs.pages.dev

View logs

[fatih-acar]

Would to be good to have a reusable workflow instead of duplicating it... can be done separately

[petercrocker]

Agreed, could use help with what the right solution/approach is here when you're bored @fatih-acar ! But this is an infrequent task, so little urgency. At least someone can figure out the work to be done now.