refactor: introduce collective liquid filter declarations

src/metaglot/__main__.py

@@ -0,0 +1,4 @@
+from . import main
+
+if __name__ == '__main__':
+    main()

src/metaglot/filters.py

@@ -0,0 +1,34 @@
+from liquid import Environment
+
+
+def _is_integer(s: str) -> bool:
+    try:
+        int(s)
+        return True
+    except (TypeError, ValueError):
+        return False
+
+
+def _is_float(s: str) -> bool:
+    try:
+        float(s)
+        return True
+    except (TypeError, ValueError):
+        return False
+
+
+def register_general_filters(env: Environment) -> None:
+    env.add_filter("to_string", str)
+    env.add_filter("format", str.format)
+    env.add_filter("to_integer", int)
+    env.add_filter("to_float", float)
+    env.add_filter("is_integer", _is_integer)
+    env.add_filter("is_float", _is_float)
+
+
+def _rc_escape(value: str) -> str:
+    return value.replace("\\", "\\\\").replace('"', '\\"')
+
+
+def register_rc_specific_filters(env: Environment) -> None:
+    env.add_filter("rc_escape", _rc_escape)