Add documentation about factorization algorithms

[codecov[bot]]

Codecov Report

Base: 84.73% // Head: 84.73% // No change to project coverage :thumbsup:

Coverage data is based on head (ab725be) compared to base (b088529). Patch has no changes to coverable lines.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #221 +/- ## ======================================= Coverage 84.73% 84.73% ======================================= Files 47 47 Lines 2975 2975 ======================================= Hits 2521 2521 Misses 454 454 ``` | [Impacted Files](https://codecov.io/gh/JuliaSmoothOptimizers/RipQP.jl/pull/221?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaSmoothOptimizers) | Coverage Δ | | |---|---|---| | [src/RipQP.jl](https://codecov.io/gh/JuliaSmoothOptimizers/RipQP.jl/pull/221/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaSmoothOptimizers#diff-c3JjL1JpcFFQLmps) | `96.07% <ø> (ø)` | | | [src/iterations/preconditioners/LDL.jl](https://codecov.io/gh/JuliaSmoothOptimizers/RipQP.jl/pull/221/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaSmoothOptimizers#diff-c3JjL2l0ZXJhdGlvbnMvcHJlY29uZGl0aW9uZXJzL0xETC5qbA==) | `83.05% <ø> (ø)` | | | [src/iterations/solvers/augmented/K2LDL.jl](https://codecov.io/gh/JuliaSmoothOptimizers/RipQP.jl/pull/221/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaSmoothOptimizers#diff-c3JjL2l0ZXJhdGlvbnMvc29sdmVycy9hdWdtZW50ZWQvSzJMREwuamw=) | `71.73% <ø> (ø)` | | | [src/iterations/solvers/augmented/K2\_5LDL.jl](https://codecov.io/gh/JuliaSmoothOptimizers/RipQP.jl/pull/221/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaSmoothOptimizers#diff-c3JjL2l0ZXJhdGlvbnMvc29sdmVycy9hdWdtZW50ZWQvSzJfNUxETC5qbA==) | `77.50% <ø> (ø)` | | | [...olvers/sparse\_fact\_utils/abstract-factorization.jl](https://codecov.io/gh/JuliaSmoothOptimizers/RipQP.jl/pull/221/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaSmoothOptimizers#diff-c3JjL2l0ZXJhdGlvbnMvc29sdmVycy9zcGFyc2VfZmFjdF91dGlscy9hYnN0cmFjdC1mYWN0b3JpemF0aW9uLmps) | `57.89% <ø> (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=JuliaSmoothOptimizers). 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=JuliaSmoothOptimizers)

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