Add Log-normal distribution

[codecov-commenter]

Codecov Report

Base: 99.94% // Head: 99.94% // Increases project coverage by +0.00% :tada:

Coverage data is based on head (6333209) compared to base (b0429d4). Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #63 +/- ## ======================================= Coverage 99.94% 99.94% ======================================= Files 27 28 +1 Lines 3338 3406 +68 ======================================= + Hits 3336 3404 +68 Misses 2 2 ``` | [Impacted Files](https://codecov.io/gh/libmir/mir-stat/pull/63?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=libmir) | Coverage Δ | | |---|---|---| | [source/mir/stat/distribution/log\_normal.d](https://codecov.io/gh/libmir/mir-stat/pull/63/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=libmir#diff-c291cmNlL21pci9zdGF0L2Rpc3RyaWJ1dGlvbi9sb2dfbm9ybWFsLmQ=) | `100.00% <100.00%> (ø)` | | | [source/mir/stat/distribution/normal.d](https://codecov.io/gh/libmir/mir-stat/pull/63/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=libmir#diff-c291cmNlL21pci9zdGF0L2Rpc3RyaWJ1dGlvbi9ub3JtYWwuZA==) | `100.00% <100.00%> (ø)` | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=libmir). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=libmir)

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