Fix documentation layout.
Fix documentation layout.

thingsboard/thingsboard.github.io,thingsboard/thingsboard.github.io,thingsboard/thingsboard.github.io,volodymyr-babak/thingsboard.github.io,volodymyr-babak/thingsboard.github.io,volodymyr-babak/thingsboard.github.io,volodymyr-babak/thingsboard.github.io,thingsboard/thingsboard.github.io