Update index.md

[sierrax369]

the linkes without .md seems not working

[clvLabs]

I just checked the links in https://clvlabs.github.io/PyATEMMax/docs/data/ and they seem to work fine... where are you trying this ?

[clvLabs]

Besides, after checking the rest of .md files, I see all of them are using the same syntax, if the change is necessary we'll have to change it in every .md file.
Please let me know if the change is necessary and I can change all of them :)

[sierrax369]

Can be a github.com problem... When you are going through the "Code" on Github to the MD File and click a link: Without the .md people get a 404, because the URI will not autocomplete.

[sierrax369]

Seem's just a blemish. I will close the pull request.

[clvLabs]

🤔
Never browsed the MD files thru the Github UI, but now that I see it it can be worth a few commits. 😃

I just created issue #26 to handle it, thanks a lot !!