docs: include popperjs to resolve jquery error on site

[flynnduism]

Changes to the docs site .js includes, to fix #2521.

Affected area:

• New Functionality [ ]
• Documentation [ ]
• Install [ ]
• Control Plane [ ]
• CLI Tool [ ]
• Certificate Management [ ]
• Networking [ ]
• Metrics [ ]
• SMI Policy [ ]
• Security [ ]
• Tests [ ]
• CI System [ ]
• Performance [ ]
• Other [ ]

Please answer the following questions with yes/no.

• Does this change contain code from or inspired by another project? If so, did you notify the maintainers and provide attribution?

[flynnduism]

This PR is still a work in progress - it's set as a draft so that the branch with the changes are deployed, making it easier to test and debug the search tool.

[bridgetkromhout]

Closing as site has moved to the osm-docs repo. Will open issue there.