Add a note about container creation cost

[roman-khimov]

Is your feature request related to a problem? Please describe.

I'm always frustrated when users don't know what's the cost of their operation.

Describe the solution you'd like

Containers cost some GAS, this should be noted on the creation page.

[roman-khimov]

It'd also be nice to auto-update NeoFS balance after this operation.

[mike-petrov]

Tell me what text to include, I don't know the exact cost

[roman-khimov]

Container cost is 0.0070000014 GAS for mainnet now.