Add sigstore (for Python)

[travishathaway]

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This pull request adds five new recipes that are all necessary in order to use the sigstore library in Python.

[conda-forge-admin]

Hi! This is the friendly automated conda-forge-linting service.

I wanted to let you know that I linted all conda-recipes in your PR (recipes/sigstore/recipe.yaml, recipes/rfc8785/recipe.yaml, recipes/sigstore-rekor-types/recipe.yaml, recipes/rfc3161-client/recipe.yaml, recipes/tuf/recipe.yaml, recipes/sigstore-models/recipe.yaml) and found some lint.

Here's what I've got...

For recipes/sigstore/recipe.yaml:

• ❌ noarch packages can't have selectors. If the selectors are necessary, please remove noarch: python.

For recipes/rfc3161-client/recipe.yaml:

• ❌ The summary item is expected in the about section.
• ❌ Non noarch packages should have python requirement without any version constraints.

For recipes/rfc3161-client/recipe.yaml:

• ℹ️ Jinja2 variable references are suggested to take a ${{<one space><variable name><one space>}} form. See lines [35].

For recipes/sigstore-models/recipe.yaml:

• ℹ️ noarch: python recipes should usually follow the syntax in our documentation for specifying the Python version.
  • For the host section of the recipe, you should usually use the pin python ${{ python_min }}.* for the python entry.
  • If the package requires a newer Python version than the currently supported minimum version on conda-forge, you can override the python_min variable by adding a Jinja2 set statement at the top of your recipe (or using an equivalent context variable for v1 recipes).

_{This message was generated by GitHub Actions workflow run https://github.com/conda-forge/conda-forge-webservices/actions/runs/22361335874. Examine the logs at this URL for more detail.}

[github-actions]

Hi! This is the staged-recipes linter and your PR looks excellent! 🚀

[conda-forge-admin]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipes/rfc8785/recipe.yaml, recipes/sigstore-models/recipe.yaml, recipes/sigstore/recipe.yaml, recipes/rfc3161-client/recipe.yaml, recipes/sigstore-rekor-types/recipe.yaml, recipes/tuf/recipe.yaml) and found it was in an excellent condition.