vignette: getting started with irg

• Input data:
  • data.table (tabular) approach vs raster
  • what's an id?
• Filtering:
  • each filter
  • filter meta
• Scaling:
  • scale_doy
  • scale_ndvi
• Modeling:
  • model_ndvi
  • nice formula
  • model_start
  • model_params
• IRG:
  • calc_irg
  • nice formula
  • irg meta

Extras:

• flowchart/steps
• irg::irg -> filter, scale, model -> ...
• alloc.col
• note: future vignettes will help with plotting + raster conversion