build: Add mypy as a dependency

requirements.txt

@@ -1,15 +1,18 @@
 attrs==23.1.0
 cattrs==23.1.2
-certifi==2023.5.7
+certifi==2023.5.7        
 charset-normalizer==3.1.0
 idna==3.4
-platformdirs==3.8.0
+mypy==1.4.1
+mypy-extensions==1.0.0   
+platformdirs==3.8.0      
 requests==2.31.0
-requests-cache==1.0.1
+requests-cache==1.0.1    
 six==1.16.0
-types-requests==2.31.0.1
+types-requests==2.31.0.1 
 types-urllib3==1.26.25.13
 types-xmltodict==0.13.0.2
+typing_extensions==4.7.0
 url-normalize==1.4.3
 urllib3==2.0.3
 xmltodict==0.13.0