Rewrite the docs

[achimnol]

Currently https://aiomonitor.aio-libs.org is from the old version.
Let's update to reflect the additions and changes from the aiomonitor-ng, such as:

• Update screencasts and screenshots
• Introduce the new commands: where-terminated, ps-terminated
• Introduce the changed method for adding custom commands to the monitor
• Describe the difference between monitor.console_locals and locals kwarg in the monitor constructor (console_locals is to inject the local variables after instantiation)