Fix point doubling, implement point addition

[codecov[bot]]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (8433eb3) 73.85% compared to head (7384857) 74.04%. Report is 1 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #172 +/- ## ========================================== + Coverage 73.85% 74.04% +0.19% ========================================== Files 47 47 Lines 3488 3533 +45 ========================================== + Hits 2576 2616 +40 - Misses 912 917 +5 ``` | [Files](https://app.codecov.io/gh/KogarashiNetwork/Kogarashi/pull/172?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=KogarashiNetwork) | Coverage Δ | | |---|---|---| | [r1cs/src/gadget/curve.rs](https://app.codecov.io/gh/KogarashiNetwork/Kogarashi/pull/172?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=KogarashiNetwork#diff-cjFjcy9zcmMvZ2FkZ2V0L2N1cnZlLnJz) | `98.61% <100.00%> (+2.31%)` | :arrow_up: | | [r1cs/src/gadget/field.rs](https://app.codecov.io/gh/KogarashiNetwork/Kogarashi/pull/172?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=KogarashiNetwork#diff-cjFjcy9zcmMvZ2FkZ2V0L2ZpZWxkLnJz) | `88.23% <100.00%> (+7.74%)` | :arrow_up: | | [r1cs/src/lib.rs](https://app.codecov.io/gh/KogarashiNetwork/Kogarashi/pull/172?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=KogarashiNetwork#diff-cjFjcy9zcmMvbGliLnJz) | `87.09% <ø> (-3.23%)` | :arrow_down: | | [r1cs/src/matrix.rs](https://app.codecov.io/gh/KogarashiNetwork/Kogarashi/pull/172?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=KogarashiNetwork#diff-cjFjcy9zcmMvbWF0cml4LnJz) | `100.00% <ø> (ø)` | | | [r1cs/src/matrix/row.rs](https://app.codecov.io/gh/KogarashiNetwork/Kogarashi/pull/172?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=KogarashiNetwork#diff-cjFjcy9zcmMvbWF0cml4L3Jvdy5ycw==) | `76.11% <100.00%> (-0.81%)` | :arrow_down: | | [zkstd/src/arithmetic/points/weierstrass.rs](https://app.codecov.io/gh/KogarashiNetwork/Kogarashi/pull/172?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=KogarashiNetwork#diff-emtzdGQvc3JjL2FyaXRobWV0aWMvcG9pbnRzL3dlaWVyc3RyYXNzLnJz) | `94.87% <100.00%> (ø)` | | | [zkstd/src/macros/curve/weierstrass.rs](https://app.codecov.io/gh/KogarashiNetwork/Kogarashi/pull/172?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=KogarashiNetwork#diff-emtzdGQvc3JjL21hY3Jvcy9jdXJ2ZS93ZWllcnN0cmFzcy5ycw==) | `80.64% <16.66%> (-15.51%)` | :arrow_down: | ... and [1 file with indirect coverage changes](https://app.codecov.io/gh/KogarashiNetwork/Kogarashi/pull/172/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=KogarashiNetwork)

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