Add missing stages to calkit objects

Author: petebachant

calkit.yaml

@@ -4,11 +4,14 @@ datasets:
   - path: data/raw/data.csv
     title: Raw data
     description: This is raw voltage data.
+    stage: collect-data
 figures:
   - path: figures/voltage-time-series.png
     title: Raw voltage time series
     description: A plot of the raw voltage time series.
+    stage: plot-voltage
 publications:
   - path: paper/paper.pdf
     title: The paper
     description: This is the paper.
+    stage: build-paper