Fix type errors and turn on type checking in CI

[paulmelnikow]

missouri/numpylib.py:29: error: Module has no attribute "bool8"  [attr-defined]
missouri/coding.py:20: error: Function is missing a type annotation  [no-untyped-def]
missouri/coding.py:29: error: Need type annotation for "method_list" (hint: "method_list: List[<type>] = ...")  [var-annotated]
missouri/coding.py:78: error: Call to untyped function "register" in typed context  [no-untyped-call]
missouri/coding.py:79: error: Call to untyped function "register" in typed context  [no-untyped-call]
missouri/coding.py:119: error: Call to untyped function "register" in typed context  [no-untyped-call]
missouri/coding.py:120: error: Call to untyped function "register" in typed context  [no-untyped-call]
missouri/test_json.py:40: error: Function is missing a type annotation for one or more arguments  [no-untyped-def]
missouri/test_json.py:48: error: Function is missing a type annotation for one or more arguments  [no-untyped-def]
missouri/test_json.py:70: error: Function is missing a type annotation for one or more arguments  [no-untyped-def]
missouri/test_json.py:78: error: Function is missing a type annotation for one or more arguments  [no-untyped-def]
missouri/test_json.py:154: error: Function is missing a return type annotation  [no-untyped-def]
missouri/test_json.py:161: error: Function is missing a type annotation  [no-untyped-def]
missouri/test_json.py:172: error: Function is missing a type annotation  [no-untyped-def]
missouri/test_json.py:180: error: Function is missing a return type annotation  [no-untyped-def]
missouri/test_json.py:187: error: Function is missing a type annotation  [no-untyped-def]
missouri/test_json.py:198: error: Function is missing a return type annotation  [no-untyped-def]
missouri/test_json.py:198: note: Use "-> None" if function does not return a value
missouri/test_json.py:206: error: Function is missing a return type annotation  [no-untyped-def]
missouri/test_json.py:206: note: Use "-> None" if function does not return a value
missouri/test_json.py:217: error: Function is missing a type annotation  [no-untyped-def]
missouri/test_json.py:228: error: Function is missing a type annotation  [no-untyped-def]
missouri/test_json.py:241: error: Function is missing a return type annotation  [no-untyped-def]
missouri/test_json.py:241: note: Use "-> None" if function does not return a value