Document different balances

[ipapandinas]

We should detail differences balances in the Token section for developers.
Here is the explanaition from a Slack message:

Thank you for bringing up the issue of balance wording on the substrate. It can indeed be tricky to understand.
To answer your question, unfortunately, we cannot update the UI as we are using the public polkadot portal instance and do not have access to the code. Therefore, it is not possible to update the UI specifically for Ternoa.

For new builders, I suggest the following:
If they use the Polkadot Portal, they must understand that on screen 1:
Total balance = Free balance + Reserved balance
Transferrable balance = Free balance - Frozen balance
Locked balance = Frozen balance
Alternatively, they can use our Indexer and the AccountEntity where:
capsAmount refers to the transferrable balance
capsFrozen refers to the locked balance
capsTotal refers to the total balance