V2 policy examples

[wooglie]

This PR adds three example policies, tests, and documentation explaining each

Fixed Issuance Policy

Fixed Issuance Policy is an example module of Marmalade which provides a simple method to program a fractional token. Because there are various ways to program fractional tokens, the contract only provides the simplest feature that is required for fractional tokens, and encourages users to extend upon the
contract.

Onchain Manifest Policy

The onchain-manifest-policy-v1 module is a part of Marmalade that provides onchain manifest storage for marmalade-v2. It implements the kip.token-policy-v2 interface and enables the management of token manifests on the blockchain.

Timed Mint Policy

The Timed Mint Policy is a module of Marmalade that enables the minting of tokens within a specific time window. This policy restricts the minting of tokens to a predefined period and provides control over the minting process.

Soul Bound Policy

Soul Bound Policy is an example module of Marmalade which provides a simple method to bind a token to an account (soul). In this context, a soul-bound token refers to a token that is uniquely associated with a specific account.

This token can be initiated, minted, and burned but not sold or transferred.

The token can be minted only once, even if the token is burned in the future.