Updating wrappers documentation (#415)

Co-authored-by: Mark Towers <mark.m.towers@gmail.com>

docs/api/wrappers.md

@@ -34,6 +34,11 @@ lastpage:
 .. autoclass:: minigrid.wrappers.FullyObsWrapper
 ```
 
+# Image Observation
+```{eval-rst}
+.. autoclass:: minigrid.wrappers.ImgObsWrapper
+```
+
 # No Death
 
 ```{eval-rst}
@@ -64,12 +69,22 @@ lastpage:
 .. autoclass:: minigrid.wrappers.RGBImgObsWrapper
 ```
 
+# RGB Partial Img Obs
+```{eval-rst}
+.. autoclass:: minigrid.wrappers.RGBImgPartialObsWrapper
+```
+
 # Position Bonus
 
 ```{eval-rst}
 .. autoclass:: minigrid.wrappers.PositionBonus
 ```
 
+# Stochastic Action
+```{eval-rst}
+.. autoclass:: minigrid.wrappers.StochasticActionWrapper
+```
+
 # Symbolic Obs
 
 ```{eval-rst}