feat: improve math with formats/parsing unit related functions

[LuizAsFight]

Improvements to math package

• now bn accepts undefined, and use default value 0 (zero)
• Added helper functions to our math bn
  • format - format units and precision. Returns a formatted value from any of BnInput
  • formatUnits - format units. Returns a formatted value from any of BnInput
  • parseUnits - create a BN instance parsing to unit value.
  • toFixed - formats a string to precision. don't consider units
• added functional shortcuts to new helpers as well

Usage (all parameters are optional):

bn('1001000000200000000').format({
  minPrecision: 3,
  precision: 8,
  units: 9
});

bn('1000000000').formatUnits(7);

bn.parseUnits('100100.00002');
bn.parseUnits('100100.00002', 5);

Closes #165

[github-actions]

Coverage report

St.❔	Category	Percentage	Covered / Total
🟢	Statements	89.66% (+0.14% 🔼)	3382/3772
🟡	Branches	70.01% (+0.09% 🔼)	649/927
🟢	Functions	86.43% (+0.11% 🔼)	675/781
🟢	Lines	89.62% (+0.15% 🔼)	3238/3613

Show new covered files 🐣

St.❔	File	Statements	Branches	Functions	Lines
🟢	... / constants.ts	100%	100%	100%	100%
🟢	math/src/decimal.ts	100%	46.15%	100%	100%
🟢	... / functional.ts	100%	100%	100%	100%

Show files with reduced coverage 🔻

St.❔	File	Statements	Branches	Functions	Lines
🟢	math/src/bn.ts	93.1% (+3.45% 🔼)	90.24% (-4.2% 🔻)	87.5% (+1.29% 🔼)	92.94% (+3.66% 🔼)

Test suite run success

515 tests passing in 46 suites.

Report generated by 🧪jest coverage report action from 14f9898

[camsjams]

Small tweaks

Re