idea: implement function call completion (limited)

parser/src/main/kotlin/gay/pizza/pork/parser/CharSourceExtensions.kt

@@ -0,0 +1,7 @@
+package gay.pizza.pork.parser
+
+fun CharSource.readToString(): String = buildString {
+  while (peek() != CharSource.NullChar) {
+    append(next())
+  }
+}