Nav bar component

**Is your feature request related to a problem? Please describe.**
In an effort to help smart contract developers get a dApp interface up and running as quickly as possible, it'd be handy for them to have a simple to use nav bar component.

**Describe the solution you'd like**
I'm thinking it could eventually include/support:
- Image (for logo)
- Title
- Customisable positioning for all these elements
- Links (for navigation)
- Dropdown links?
- `Button` for "Connect" CTA etc
- Enhanced ETH address for "identity"/"profile" connected state
- Responsive mobile menu

Rough examples:

**Additional context**
https://bulma.io/documentation/components/navbar/