Add `zkuzmic/which-jspm`

[unixorn]

Description

Add zkuzmic/which-jspm now that https://github.com/zkuzmic/which-jspm/issues/2 is closed

Closes https://github.com/zkuzmic/which-jspm/issues/2

Type of changes

• [ ] A link to an external resource like a blog post
• [ ] Add/remove/update a link to a framework
• [x] Add/remove/update a link to a plugin
• [ ] Add/remove/update a link to a tab completion
• [ ] Add/remove/update a link to a theme
• [ ] Text cleanups/typo fixes

Copyright Assignment

• [x] This document is covered by the BSD License, and I agree to contribute this PR under the terms of the license. This is for the list submission, not for the project(s) you're adding, I don't care what license the plugins have as long as they have something.

Checklist:

• [x] I have read the CONTRIBUTING document.
• [x] All new and existing tests passed.
• [x] I have confirmed that the link(s) in my PR is valid.
• [x] I have signed off my commits. You can use git commit --amend --no-edit --signoff to amend an existing commit, and you can find more details about signing off commits on the DCO GitHub action page here
• [x] My entries are single lines and are in the appropriate (plugins, themes, or completions) section, and in alphabetical order in their section.
• [ ] Any added completions have a readme and a license file in their repository.
• [ ] Any added frameworks have a readme and a license file in their repository.
• [x] Any added plugins have a readme and a license file in their repository.
• [ ] Any added themes have a screenshot, a readme, and a license file in their repository.
• [x] I have stripped any leading and/or trailing zsh-, zsh-plugin and/or oh-my-zsh- substrings from the link name. This makes it easier to find plugins/themes/completions by name by preventing big clusters in the O and Z sections of the list.