Typos in Contributing.md and issue template

[rupav]

I'm submitting a ... (check one with "x")

• [x] bug report
• [ ] feature request
• [ ] support request => Please do not submit support requests here, instead ask your query in out Gitter channel at https://gitter.im/fossasia/susi_server

Current behavior:

Couple of typos in above templates/files. Expected behavior:

No mistakes. Steps to reproduce:

Would you like to work on the issue? Yes.