Selecting text using mouse and new abstraction for cursors

src/text_editor/buffer.cpp

@@ -76,6 +76,13 @@ Range GetEnd(const Buffer &buffer) {
     return range;
 }
 
+Range MakeRange(int64_t a, int64_t b) {
+    Range result = {};
+    result.min   = Min(a, b);
+    result.max   = Max(a, b);
+    return result;
+}
+
 void AddEdit(Array<Edit> *edits, Range range, String string) {
     edits->add({range, string});
 }