docs: note about existing content at same path on different branches

vintro

2023-08-14 f1c9ca495e450ecb62dade70c4b60d86e106f79c

 quartz/styles/base.scss

@@ -11,7 +11,8 @@
  width: 100vw;
}

body, section {
body,
section {
  margin: 0;
  max-width: 100%;
  box-sizing: border-box;