feat: units utils

[tabaktoni]

Motivation and Resolution

Requested by dev from HH Bangkok similar to https://viem.sh/docs/utilities/formatUnits

Convert fri to strk

units(1n, 'fri')

convert strk to fri

units('0.3', 'strk')

Checklist:

• Performed a self-review of the code
• Rebased to the last commit of the target branch (or merged it into my branch)
• Linked the issues which this PR resolves
• Documented the changes in code (API docs will be generated automatically)
• Updated the tests
• All tests are passing

[tabaktoni]

@penovicp plc check did i overengineer and did I miss some cases

[PhilippeR26]

lgtm.
Just the orthography ofsimbol

[penovicp]

Aside from the simbol/symbol issue that Phil mentioned, the PR mostly looks good to me.

The only thing I would suggest is to split the new function into two complementary ones, something like formatStrkToFri() and formatFriToStrk(). I feel that approach would be less ambiguous and more discoverable.

I'll approve the PR and let you decide.

[PhilippeR26]

The current function signature is just a copy of Ethers ones.
It allows an easy transition to Starknet for EVM guys.