Set a CSP in the html meta tags for search multiple erddaps

[ChrisJohnNOAA]

Description

Adds a hardcoded CSP to the search multiple erddaps page. This should allow the page to fully function without needing to adjust the CSP for the entire server.

Type of change

Please delete options that are not relevant.

• [ X ] Bug fix (non-breaking change which fixes an issue)

Checklist before requesting a review

• [ X ] I have performed a self-review of my code
• [ X ] My code follows the style guidelines of this project
• [ X ] I have commented my code, particularly in hard-to-understand areas
• [ X ] I have made corresponding changes to the documentation
• [ X ] My changes generate no new warnings
• [ X ] I have added tests that prove my fix is effective or that my feature works
• [ X ] New and existing unit tests pass locally with my changes