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

vintro

2023-08-14 f1c9ca495e450ecb62dade70c4b60d86e106f79c

 quartz/components/styles/footer.scss

@@ -1,6 +1,7 @@
footer {
  text-align: left;
  margin-bottom: 4rem;
  opacity: 0.7;

  & ul {
    list-style: none;