Format with Fantomas, and add MIT licence

.editorconfig

@@ -0,0 +1,13 @@
+root = true
+
+[*.fs]
+fsharp_space_before_uppercase_invocation=true
+fsharp_space_before_member=true
+fsharp_space_before_parameter=true
+fsharp_space_before_colon=true
+fsharp_space_before_semicolon=true
+fsharp_multiline_block_brackets_on_same_column=true
+fsharp_newline_between_type_definition_and_members=true
+fsharp_keep_if_then_in_same_line=true
+fsharp_align_function_signature_to_indentation=true
+fsharp_alternative_long_member_definitions=true