Add identity lift function

[Bronek]

Also drive-by fix in transform.hpp

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 100.0%. Comparing base (4a8e479) to head (3c5727f).

Additional details and impacted files

[](https://app.codecov.io/gh/libfn/functional/pull/76?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=libfn) ```diff @@ Coverage Diff @@ ## main #76 +/- ## ======================================= Coverage 100.0% 100.0% ======================================= Files 20 20 Lines 857 857 Branches 121 121 ======================================= Hits 857 857 ``` | [Files](https://app.codecov.io/gh/libfn/functional/pull/76?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=libfn) | Coverage Δ | | |---|---|---| | [include/functional/pack.hpp](https://app.codecov.io/gh/libfn/functional/pull/76?src=pr&el=tree&filepath=include%2Ffunctional%2Fpack.hpp&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=libfn#diff-aW5jbHVkZS9mdW5jdGlvbmFsL3BhY2suaHBw) | `100.0% <ø> (ø)` | | | [include/functional/transform.hpp](https://app.codecov.io/gh/libfn/functional/pull/76?src=pr&el=tree&filepath=include%2Ffunctional%2Ftransform.hpp&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=libfn#diff-aW5jbHVkZS9mdW5jdGlvbmFsL3RyYW5zZm9ybS5ocHA=) | `100.0% <ø> (ø)` | | [](https://app.codecov.io/gh/libfn/functional/pull/76?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=libfn)