Implement query plugins

[granludo]

Implement two new query plugins:
[ ]: Only content query plugin. Which will return the data as a markdown string :
"# Source 1:
{source content text}

Source 2:

{source content text}

.... "
[ ]: Markdown content and metadata plugin. Which will return the data as a markdown string:

Source 1

Source 1 Metadata

• Similitude:
• Import plugin and settings
• Filename:
• URL (if existing):

Custom Metadata

Contents

-> LAMB Custom Augment functions can be parametrized with variables from the context