Create the exercise specs on cyclomatic complexity

This MR adds the exercise specification about cyclomatic complexity and
control flow graph (CFG).

Closes #4.

See merge request !5

Create the exercise specs on input domain modeling

This MR adds the exercise specification about creating an input domain model.

Closes #3.

See merge request !4

Use Material for MkDocs theme

This MR switches the theme used on the website from default to Material for MkDocs.

Closes #9.

See merge request !3

Create the exercise specs on creating a CI pipeline

This MR adds the exercise specification about creating a CI pipeline.

Closes #2.

See merge request !2

Setup CI pipeline to automate the build and deploy processes

See merge request !1