Lognormal Inv cdf

[DoganCK]

Thank you for contributing to FSharp.Stats. Please take the time to tell us a bit more about your PR.

Please reference the issue(s) this PR is related to

262 (an addition to it, doesn't close)

Please list the changes introduced in this PR

• Inv CDF function for the lognormal

Description

Uses the exponent of the normal inverse CDF functions which mimics the implementation both in scipy.stats and R.

Tested against qlnorm from R.

[Required] please make sure you checked that

• [x] The project builds without problems on your machine

[Optional]

• [x] Added unit tests regarding the added features