Lines in markdown files are too long, discuss.md is missing

[bencomp]

The automatic checks on pull requests produced warnings on a missing file and the length of lines in several markdown files:

Missing required file ./_extras/discuss.md
./README.md: Line(s) too long: 1, 2
./_episodes/01-introduction.md: Line(s) too long: 21, 22, 24, 25, 26, 35, 39, 43, 49, 50, 51, 52
./_episodes/02-working-with-openrefine.md: Line(s) too long: 28, 30, 33, 34, 36, 39, 41, 46, 47, 48, 50, 56, 61, 63, 71, 72, 73, 78, 79, 84, 88, 94, 96, 97, 113, 117, 118, 119, 120, 125, 128, 130, 131, 132, 133, 134, 136, 141, 147, 150, 153, 155, 157, 172, 175, 206, 214, 218, 219, 220, 221, 227, 229, 232, 233
./_episodes/03-filter-sort.md: Line(s) too long: 20, 22, 23, 32, 34, 42, 44, 46, 56, 58, 60, 71, 73, 80, 85, 93, 95, 99, 102, 103, 104, 108, 112
./_episodes/04-numbers.md: Line(s) too long: 19, 21, 23, 27, 31, 32, 38, 42, 43, 44, 48
./_episodes/05-scripts.md: Line(s) too long: 20, 21, 22, 27, 31, 35, 37, 38, 41
./_episodes/06-saving.md: Line(s) too long: 20, 25, 30, 34, 35, 36, 40, 41, 42, 46, 47, 53, 54, 57
./_episodes/07-resources.md: Line(s) too long: 18, 23, 24, 29, 30, 32
./_extras/guide.md: Line(s) too long: 8, 12, 13, 20, 32, 37, 47, 52
./reference.md: Line(s) too long: 7, 12, 15, 18, 24, 27, 30, 33, 42
./setup.md: Line(s) too long: 21, 39, 45, 46, 47, 53, 59, 60, 61, 66, 73
Problems detected but ignored (permissive mode).

These are not very important problems, but long lines may indeed make editing the text a bit of a hassle.
The maximum line length set in .editorconfig and bin/lesson_check.py is 100 characters for markdown files.

I'd happily accept PRs that update individual files.

[bencomp]

With regards to the missing _extras/discussion.md file: https://carpentries.github.io/lesson-example/03-organization/index.html explains what it should be:

General discussion of the lesson contents for learners who wish to know more: This page normally includes links to further reading and/or brief discussion of more advanced topics.

1. Its title must be "Discussion".
2. It may include whatever content the author thinks appropriate.

It looks like 'we' cover those topics in our episodes 1 and 7.