[UX] The default view for hypercerts should be 'only evaluated'

[bitbeckers]

Describe the feature you'd like to request

As an user, I want to be able to easily inspect valid hypercerts, so that I can explore which impact I want to fund

Describe the solution you'd like

The current explore page uses search parameters to determine the applied filter. The default of this should be 'only evaluated' so that then a user goes to app.hypercerts.org/explore they only see evaluated hypercerts.

Describe alternatives you've considered

Linking to explore and forwarding to /explore?filter=only-evaluated but that wouldn't apply to external parties linking to /explore

[tnkshuuhei]

will work on after #387 has solved