Add th_cheb2jac and th_jac2cheb

[codecov[bot]]

Codecov Report

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

Comparison is base (5028278) 83.04% compared to head (48ff1e2) 83.33%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #229 +/- ## ========================================== + Coverage 83.04% 83.33% +0.29% ========================================== Files 15 15 Lines 2772 2809 +37 ========================================== + Hits 2302 2341 +39 + Misses 470 468 -2 ``` | [Files](https://app.codecov.io/gh/JuliaApproximation/FastTransforms.jl/pull/229?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaApproximation) | Coverage Δ | | |---|---|---| | [src/toeplitzhankel.jl](https://app.codecov.io/gh/JuliaApproximation/FastTransforms.jl/pull/229?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaApproximation#diff-c3JjL3RvZXBsaXR6aGFua2VsLmps) | `96.80% <100.00%> (+0.73%)` | :arrow_up: |

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