fixed a typo in a link to documentation in README.md file

[pzaino]

This PR contains:

• [ ] bugfix
• [ ] feature
• [ ] refactor
• [x] documentation
• [ ] other

Are tests included?

• [x] no
• [ ] yes (bugfixes and features will not be merged without tests)

Breaking Changes?

• [x] no
• [ ] yes (breaking changes will not be merged unless absolutely necessary – please provide motivation)

List any relevant issue numbers:

Description