Add code coverage

requirements/ci.txt

@@ -0,0 +1,7 @@
+certifi==2020.11.8
+chardet==3.0.4
+codecov==2.1.10
+coverage==5.3
+idna==2.10
+requests==2.25.0
+urllib3==1.26.2

requirements/test.txt

@@ -0,0 +1,13 @@
+attrs==20.3.0
+coverage==5.3
+iniconfig==1.1.1
+packaging==20.4
+pluggy==0.13.1
+py==1.9.0
+pyparsing==2.4.7
+pytest==6.1.2
+pytest-aiohttp==0.3.0
+pytest-cov==2.10.1
+six==1.15.0
+toml==0.10.2
+typing-extensions==3.7.4.3