feat: add `/networks` api

[pdp2121]

High Level Overview of Change

Add \networks endpoint to display all networks/ sidechains on VHS database. Would be useful for internal development, other API calls, and DID tooling.

Type of Change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Refactor (non-breaking change that only restructures code)
• [ ] Tests (You added tests for code that already exists, or your new feature included in this PR)
• [ ] Documentation Updates
• [ ] Release

[mvadari]

nit: the / is the wrong way in the PR title