Typos in 02_sampling/sTDEP tutorial

[corettialessandro]

Check the following typos in README.md file:

1. lines 10 and 30: generature_structure -> generate_structure
2. line 70: extract_forceconsants' -> extract_forceconstants`

[m-a-saleh]

Another typo:
in generate_structure under "Examples"
generate_structure -dim 4 3 5 -> generate_structure -d 4 3 5