Issues with CONTRIBUTING.md guide

[davidekete]

The CONTRIBUTING.md guide uses a lot of placeholders that are not clearly distinguished. Conventionally, placeholders in code blocks are depicted with curly braces ({}), enclosed angle brackets (<>), or all uppercase. This is not the case in the guide as the placeholders in all the code blocks look don't look like such.

Describe the solution you'd like
Differentiate placeholders from the actual commands.