Restrict zarr and tifffile versions (#237)

Tifffile's zarr integration doesn't support zarr 3, and we are
using a tifffile feature that's been discontinued in the
latest version. This change restricts those packages'
versions to compatible ones, as provides in the installation
instructions in the README and documentation.

Author: jmuhlich

README.md

@@ -105,7 +105,7 @@ conda activate ashlar
 
 In the activated environment, install dependencies and ashlar itself:
 ```bash
-conda install -y -c conda-forge numpy scipy matplotlib networkx scikit-image scikit-learn tifffile zarr pyjnius blessed
+conda install -y -c conda-forge numpy scipy matplotlib networkx scikit-image scikit-learn "tifffile<2025.2.18" "zarr<3" pyjnius blessed
 pip install ashlar
 ```
 

docs/instructions/installation.md

@@ -34,7 +34,7 @@ conda activate ashlar
 
 In the activated environment, install dependencies and ashlar itself:
 ```bash
-conda install -y -c conda-forge numpy scipy matplotlib networkx scikit-image scikit-learn tifffile zarr pyjnius blessed
+conda install -y -c conda-forge numpy scipy matplotlib networkx scikit-image scikit-learn "tifffile<2025.2.18" "zarr<3" pyjnius blessed
 pip install ashlar
 ```