Side exercises can only be unlocked by core exercises. Previously we
had exercises being unlocked by both core and side exercises.

Each core exercise should unlock at least one exercise. Previously we
had some core exercises that didn't unlock any side exercises. Now
that's only true of the last core exercise in the track.

Show Smarticles101's bio on the website

Fixes #647 use typed empty lists

Add echo's to run-journey-test-from-ci for debug info

Potential solve for #326 and journey-test passing when they fail

Add tests to catch invalid input edge cases

Fixes #745 correct spelling mistake

Fixes #714 assertTrue -> assertEquals

Add default introductory code example

Instead of having logic for a fallback in the backend, we're choosing a
default for the snippet file.

For tracks that have core exercises, we pick the first core exercise.
For tracks without these, we pick the first exercise listed in the config.

Implement suggestions from #410

Move README includes

Fixes #718

Per
https://github.com/exercism/docs/blob/ccdf58f97f698c265f0f67fa7cb9d94084d7f0a3/language-tracks/exercises/README.md#files

change: update to v1.1.0 tests

Move readme insert

Fixes #720 replace lambda with method ref

This reverts commit 43e792bf55f3e53ae696b8480ba8fe73bac5bba0.

Remove unused images

Fixes #716 remove redundant type params

Fixes #696

Fixes #737

Use string builder over looped string concatenation.