Fix broken links to Gitter Community

[ChVeen]

What would you like to share?

It seems that the link https://gitter.im/TheAlgorithms as used in the README.md and CONTRIBUTING.md files is invalid.
I get the error 404 Not Found.

Additional information

No response

[KaixLina]

it took me a while to find this issue because ....the loc of the issue is not stated clearly in the above issue request .....i will try to find the sol....

[ChVeen]

Hi @KaixLina please note that this issue is already solved, see pull request #8546.