[FEATURE] Filter Keywords prebuilt preset

[jmbannon]

Adds Filter Keywords, a preset that can include or exclude media with any of the listed keywords. Both keywords and title/description are lower-cased before filtering.

Supports the following override variables:

• title_include_keywords
• title_exclude_keywords
• description_include_keywords
• description_exclude_keywords

For best usage, use the ~ tilda subscription mode to set a subscription's list override variables.
Tilda mode allows override variables to be set directly underneath it.

Plex TV Show by Date | Filter Keywords:
  
  = Documentaries:
    "~NOVA PBS":
       url: "https://www.youtube.com/@novapbs"
       title_exclude_keywords:
         - "preview"
         - "trailer"  

    "~To Catch a Smuggler":
       url: "https://www.youtube.com/@NatGeo"
       title_include_keywords:
         - "To Catch a Smuggler"