feat(lcd): add fill and antialias support for line graphs

[dogukanveziroglu]

Hi,
I've been using this project for my setup and wanted the line graphs to look more like Windows Task Manager / Linux Mission Center - with filled areas under the lines and smoother edges.

So I added three new optional parameters to LINE_GRAPH:

• FILL: Fill the area under the line
• FILL_COLOR: RGBA color with transparency support
• ANTIALIAS: 2x supersampling for smoother lines

Example usage in theme.yaml:

LINE_GRAPH:                                                                                                                                                                                                                                                                    
  FILL: True                                                                                                                                                                                                                                                                   
  FILL_COLOR: 0, 180, 216, 80                                                                                                                                                                                                                                                  
  ANTIALIAS: True

Screenshots:

Before:

After: