feat: update dependencies, add linting, fix codebase, cleanup (#11)

* chore(deps): update dependencies

* feat(tests): add matrix testing, problem matcher

* feat(lint): add php-cs-fixer, fix codebase

.editorconfig

@@ -0,0 +1,16 @@
+# EditorConfig is awesome: https://editorconfig.org
+
+# top-most EditorConfig file
+root = true
+
+[*]
+end_of_line = lf
+insert_final_newline = true
+charset = utf-8
+indent_style = space
+indent_size = 4
+max_line_length = 100
+
+[*.yml]
+indent_size = 2
+