Fixed few typos in the documentation

[ImadSaddik]

While reading the Run and Qrels pages, I found the same typo in the save section that I fixed.

Before

File type is automatically inferred `form` the filename extension ...

After

File type is automatically inferred `from` the filename extension ...

I found another typo in the Report page.

Before

... and exporting those `il` LaTeX for ...

After

... and exporting those `in` LaTeX for ...

In index.md, I fixed a broken link and another typo.

Before

[Weighted Sum](https://amenra.github.io/ranx/fusion/`#wighted-sum`)

After

[Weighted Sum](https://amenra.github.io/ranx/fusion/`#weighted-sum`)

And finally, I found another typo in fusion.md

Before

### LogN_ISR
Computes `Log_ISR` as proposed by [Mourão et al.](https://www.sciencedirect.com/science/article/abs/pii/S0895611114000664).

After

### LogN_ISR
Computes `LogN_ISR` as proposed by [Mourão et al.](https://www.sciencedirect.com/science/article/abs/pii/S0895611114000664).

Thank you for making ranx, I really love this project and I am happy to contribute.