Add recipe for the "multispline" package

[mpigou]

Checklist

• Title of this PR is meaningful: e.g. "Adding my_nifty_package", not "updated meta.yaml".
• License file is packaged (see here for an example).
• Source is from official source.
• Package does not vendor other packages. (If a package uses the source of another package, they should be separate packages or the licenses of all packages need to be packaged).
• If static libraries are linked in, the license of the static library is packaged.
• Package does not ship static libraries. If static libraries are needed, follow CFEP-18.
• Build number is 0.
• A tarball (url) rather than a repo (e.g. git_url) is used in your recipe (see here for more details).
• GitHub users listed in the maintainer section have posted a comment confirming they are willing to be listed there.
• When in trouble, please check our knowledge base documentation before pinging a team.

[github-actions]

Hi! This is the staged-recipes linter and I found some lint.

File-specific lints and/or hints:

• recipes/multispline/meta.yaml:
  • lints:
    • The following maintainers have not yet confirmed that they are willing to be listed here: znasipak. Please ask them to comment on this PR if they are.

[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/multispline/meta.yaml) and found it was in an excellent condition.

[znasipak]

I confirm that I will be a recipe maintainer

[github-actions]

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

[mpigou]

@conda-forge/help-python-c, ready for review!

[mpigou]

@conda-forge-admin, please ping conda-forge/help-python-c

[conda-forge-webservices]

Hi! This is the friendly automated conda-forge-webservice.

I was asked to ping @conda-forge/help-python-c and so here I am doing that.