Add 8 new exercices and format Roc code

[ageron]

This PR adds 8 new exercises:

• bottle-song
• dnd-character
• grade-school
• line-up
• resistor-color-trio
• save-the-cow
• simple-cipher
• twelve-days

Note: the simple-cipher exercise does not have a template.j2. This just means that if the test specs ever change, we will need to update simple-cipher-test.roc by hand.

[github-actions]

This PR touches files which potentially affect the outcome of the tests of an exercise. This will cause all students' solutions to affected exercises to be re-tested.

If this PR does not affect the result of the test (or, for example, adds an edge case that is not worth rerunning all tests for), please add the following to the merge-commit message which will stops student's tests from re-running. Please copy-paste to avoid typos.

[no important files changed]

For more information, refer to the documentation. If you are unsure whether to add the message or not, please ping @exercism/maintainers-admin in a comment. Thank you!

[ageron]

Note: since I ran roc fmt on all .roc files in this repo, a few existing exercises were slightly modified (essentially replacing -> with |> and changing a few indentations). Since these changes are superficial, I think we should add [no important files changed] to the merge-commit message when the PR is merged.

[Anton-4]

Looks good @ageron!