[docs] Devdocs Bootstrap font utilities refactor

Author: roland04

docs/guides/bs5migration/index.md

@@ -278,3 +278,24 @@ The `.close` class has been replaced with `.btn-close`.
 ```
 
 </ValidExample>
+
+### Font utility classes
+
+The `.font-weight-*` class has been replaced with `.fw-*` for brevity and consistency.
+The `.font-italic` class has been replaced with `.fst-italic` for brevity and consistency.
+
+<InvalidExample title="Don't">
+
+```html
+<span class="font-weight-bold font-italic">I'm a bold italic text</span>
+```
+
+</InvalidExample>
+
+<ValidExample title="Do">
+
+```html
+<span class="fw-bold fst-italic">I'm a bold italic text</span>
+```
+
+</ValidExample>