Add IOG contracts

[ChristianoBraga]

• Milestone 2 requires the execution and verification of ERC20-like contracts in KPlutus. The closest element in Cardano is a native token minting policy. Milestone 3 is set to a best effort audit, using KPlutus, of the DJED protocol: an algorithmic stablecoin dApp.

• This commit adds directory IOG-contracts. Under this directory there are 2 subdirectories: native-tokens and stablecoin. Directory native-tokens has two contracts and some files to generate UPLC code from their minting policies and traces of their execution. Directory stablecoin has one contract, an implementation of MiniDJED, a DJED prototype, and similar scripts for UPLC code generation.

• There are README.md files under IOG-contracts and for each subdirectory explaining their contents and how to generate UPLC code from them.

[SchmErik]

nevermind, I saw that they've been addressed.