[ENH] Add verification for member buckling and combined flexural and lateral torsional buckling

**Describe the solution you'd like**
A function that takes as input a cross section, member length, support conditions and the member actions / loading type (moment, shear, normal force) and performs all of the verfications required by Eurocode 3 for a strucutral member.

Combined flexural buckling should be considered e.g. following EC3-1-1 §6.3.3

**Describe alternatives you've considered**

**Additional context**