Add docker build steps to read-me for compiling locally with docker

[mathew-fleisch]

• Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• [NA] Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

This change adds instructions for building locally with docker.

• What is the current behavior? (You can also link to an open issue here)

There is no behavior change, only documentation changes.

• What is the new behavior (if this is a feature change)?

There is no behavior change, only documentation changes.

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)

No.

• Other information: