refactor: modify finish exercise workflow to overwrite README and use reusable workflow from exercise-toolkit

[FidelusAleksander]

Summary

Used the release v0.3.0 of exercise toolkit for start and finish exercise workflows.

Repository README is now updated entirely based on a reusable template after the exercise is started and finished.

Changes

Closes:

Task list

• For workflow changes, I have verified the Actions workflows function as expected.
• For content changes, I have reviewed the style guide.

[Copilot]

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

Comments suppressed due to low confidence (1)

.github/workflows/4-copilot-on-github.yml:93

• Ensure that '${{github.workflow}}' expands to the intended workflow name when disabling it; if the workflow name contains spaces or unexpected characters, this may lead to issues in properly disabling the active workflow. Consider testing this behavior or using an explicit workflow identifier if necessary.

run: gh workflow disable "${{github.workflow}}"