Update JavaScript dependencies and their versions#

There are two kinds of dependency definitions in this theme:

package.json contains the base dependencies for this theme. They are broken down into a few categories like dependencies and devDependencies. It is edited by the maintainers.
package-lock.json contains the complete frozen dependency chain for this theme, including all sub-dependencies of our base dependencies. It is automatically generated.

To update or add a JS dependency, follow these steps:

Edit package.json by adding or modifying a dependency.
Re-generate package-lock.json in order to create a new set of frozen dependencies for the theme. To do this, run the following command from the Sphinx Theme Builder.
```
stb npm install --include=dev
```
Commit both files to the repository. When new people pull in the latest commits, their npm environment will automatically update according to the new lockfile.