[docs] added notes about extra dependencies

Author: MrClock8163

README.md

@@ -55,7 +55,11 @@ cd Instrumentman
 python -m pip install .
 ```
 
+Some commands require additional dependencies, that are not installed by
+default with I-man. These are indicated in the documentations of the specific
+commands.
+
 ## License
 
-I-man is free and open source software, and it is distributed under the terms of the
-[MIT License](https://opensource.org/license/mit).
+I-man is free and open source software, and it is distributed under the terms
+of the [MIT License](https://opensource.org/license/mit).

src/instrumentman/panorama/__init__.py

@@ -416,6 +416,8 @@ def cli_calc(**kwargs: Any) -> None:
     Merge previously captured panorama frames and optionally annotate measured
     points on the resulting panorama for documentation purposes.
 
+    IMPORTANT: This command requires an extra dependency: 'opencv-python'
+
     The individual images are transformed into an equirectangular projection
     based on the orientation metadata saved at the time of acquisition. The
     projected images are then merged into a single panorama image.