ENH: add back in ssd_inventory (#148)

Author: mmcky

lectures/_toc.yml

@@ -24,7 +24,7 @@ parts:
  - file: short_path
  - file: opt_invest
  - file: opt_savings
- # - file: inventory_ssd
+ - file: inventory_ssd
  - file: ifp_egm
  - file: arellano
  - file: aiyagari_jax