alicelieutier/smoothScroll

- Adds no-font-awesome variable to template to turn off remote FA
- FA is added in header as <script defer> for header buttons
- fa_icon() will include the rmarkdown FA dependency

- compact() returns NULL if all elements are NULL
- map_arg handles no .args provided
- is_htmlish() actually works now

- Now works like bulma_column(), doesn't re-wrap level items
- Export bulma_level_item() and functions for header level items
- map_arg now takes multiple arguments, and drops null .args
- Adds tag_[div|p|a]()
- Adds c_str()