Release version 0.12.15 (#938)

Update project version to 0.12.15 in pyproject.toml and README. Adjust installation instructions to reference the new version tag.

Author: LeMyst

README.md

@@ -355,10 +355,10 @@ python -m pip install .
 If you want to install a specific branch or tag from the repository, you can use the following command:
 
 ```bash
-python -m pip install git+https://github.com/LeMyst/WikibaseIntegrator.git@v0.12.14
+python -m pip install git+https://github.com/LeMyst/WikibaseIntegrator.git@v0.12.15
 ```
 
-where `v0.12.14` is the tag or branch you want to install.
+where `v0.12.15` is the tag or branch you want to install.
 
 You can also use Poetry:
 

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "WikibaseIntegrator"
-version = "0.12.15.dev0"
+version = "0.12.15"
 description = "Python package for reading from and writing to a Wikibase instance"
 authors = [
     "Myst",