htmldf todo

[alastairrushworth]

• add code column using text classifier
  • simple test set for future improvements
  • add training script to repo and to .Rbuildignore
  • test for r / python code inference
  • check correct behaviour when no code tags
  • code tags types up to date?
• train code text classifier: R, Python
• datetime accessed
• social column of tibbles : add other sites
• loop once only over rows
• add webpage publication date