Expand `Overview` on Homepage

This should be filled out similar to https://namada.valopers.com/ and https://explorer75.org/namada with important network stats. There can be some overlap with what is on https://metrics.namada.net

Starter ideas:
- Total supply NAM
- Non-native TVL of MASP
- Total tokens staked (with percentage)
- Total txs (shielded + all)
- Time estimate of next epoch
- Inflation rates
- PGF balance