Add doc option

[Chemaclass]

📚 Description

Right now all assertions can be found in the website https://bashunit.typeddevs.com/assertions The goal is to enable finding those assertions from the ./bashunit directly

🔖 Changes

• Add --doc [filter] option

✅ To-do list

• [x] I updated the CHANGELOG.md to reflect the new feature or fix
• [x] I updated the documentation to reflect the changes

🖼️ Demo

⚠️ Problem

The current problem is that the built is a standalone executable, so there is no access to "docs/assertions.md"... we have to find another way 🤔