Pull Request carpentries/styles#330
Closes carpentries/styles#343

1. Fix the script so that all figures are displayed.
2. Add image numbers.
3. Don't add headers for episodes without images.
4. Add horizontal rulers to better separate adjacent images.
   Don't add a ruler after the last image in the episode.
5. Add empty lines to `figures.md` to improve code readability.
6. Use classes for styling text and figures

Pull Request: carpentries/styles#327

Pull Request: carpentries/styles#216

Pull Request: carpentries/styles#323

Close carpentries/styles#325

added workshop calendar

space out callout elements better

Fix lesson_initialize.py to initialize new lessons

CODE_OF_CONDUCT.md is already at the root of the repository.

Add surveys

Makefile: fix typo in clean-rmd rule

fix survey link variables

added about the discussion stage to the LC description

[fix carpentries/styles#311] update descriptions of the carpentries

Pull Request: carpentries/styles#313

Check that Rmd episode files include `source: Rmd`

Fixes carpentries/styles#273

links.md: add links to carpentries' lessons overview pages