Is the main landing gear of a large airplane designed for sideways (crabbed) touchdowns?
The landing gear is indeed designed to cope with crabbed crosswind landings.  

The recommendation is to avoid crab on landing however in severe crosswind conditions it is sometimes impossible to decrab completely without introducing excessive bank. Therefore some residual crab has to be allowed. 

Airbus recommends less then 5 degrees of residual crab on landing, but aircraft are designed to cope with more. 

An exceptional design is found in the B-52, where the main landing gear can rotated to be aligned with the direction of travel to deal with extreme crab angles.