Cheat Sheet: define font sizes relative to container, not root

This allows overriding the font sizes for the Cheat Sheet specifically
when printing.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

assets/sass/cheat-sheet.scss

@@ -9,19 +9,19 @@
     border-radius: 10px;
     border: 1px solid var(--callout-color);
     display: flex;
-    font-size: 1rem;
+    font-size: 1em;
     flex-direction: column;
     gap: 5px;
 
     p {
-      font-size: 1rem;
+      font-size: 1em;
       margin: 0 8px;
     }
 
     h3 {
       color: var(--font-color);
       line-height: 1em;
-      font-size: 1.1rem;
+      font-size: 1.1em;
       margin-bottom: 8px;
       font-weight: 500;
     }
@@ -71,7 +71,7 @@
       grid-column: 1/3;
 
       margin-top: 0;
-      font-size: 1.2rem;
+      font-size: 1.2em;
       font-weight: 700;
       line-height: 1.2;
       color: var(--orange);