Fix RTL swipe direction

[omarchehab98]

What did you do:

Fixed RTL swipe direction by negating dx and vx in the methods that calculate the offset.

Does this relate to any issue(s)? If so which one(s)?

Issue #26

Screenshots:

Checklist:

• I added link to related issue if there is one
• I added a screenshot/gif (if appropriate)
• [ ] I ran yarn lint and yarn flow

[omarchehab98]

I skipped running yarn lint and yarn flow because yarn lint editing many things other than my code, yarn flow throw errors not relevant to my commit.