implement dwim indenting with tab, s-tab
implement dwim indenting with tab, s-tab

- note
  - wanted to additionally configure imap
    - e.g.
      - | imap <Tab> <C-O><Tab>
        | imap <S-Tab> <C-O><S-Tab>
    - but would require elaborate implementation to handle insert mode
      newline case
      - i.e.
        - cursor jumps to start of empty line where tabbing has no effect

atweiden/pacfiles,atweiden/pacfiles