feat: flow examples

[andreivladbrg]

Closes #36

Note: this PR merge must be synchronized with docs reference changes due to v2 rename to lockup (e.g. this one). Will work on that once you finish with your refactor @smol-ninja.

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The flow example contracts are represented by these 4:

1. FlowBatchable
   • different functions (adjustRatePerSecondAndDeposit, createMultiple, createAndDepositViaBroker etc.) to declare the calldata as bytes for multiple function calls into a single tx
2. FlowManager
   • Manager contract that calls function to manage streams (basically mirror functions)
3. FlowStreamCreator
   • Contract for creating 2 streams with different rates
4. FlowUtilities
   • A library (used in the stream creator contract) with a series of utility functions for calculating the rps using a desired amount and duration.

@sablier-labs/solidity lmk if you have anything else in mind, or if the current ones should suffice

[smol-ninja]

@andreivladbrg this might need some refactor with the deposit function

[andreivladbrg]

@andreivladbrg this might need some refactor with the deposit function

indeed it needs, will updated it

also, since the repo is public now, it can be removed via package.json file so the gitmodules can be removed