docs: Update documentation about MPD alternate (#7502)

Author: avelad

README.md

@@ -313,6 +313,7 @@ Shaka Player supports:
 - AWS MediaTailor for Server-Side
 - AWS MediaTailor overlays
 - HLS interstitials
+- DASH Media Presentation Insertion (MPD alternate)
 - Custom Interstitials
 - Basic support of VAST and VMAP without IMA (playback without tracking)
 

docs/tutorials/ad_monetization.md

@@ -65,6 +65,7 @@ Note: overlays ad insertions is the same as server side.
 
 Shaka Player supports different types of interstitials:
  - HLS Interstitials
+ - DASH Media Presentation Insertion
  - Custom Interstitials
  - VAST (playback without tracking)
  - VMAP (playback without tracking)
@@ -76,6 +77,12 @@ It is not necessary to do anything, Shaka Player supports it natively without
 any type of intervention.
 
 
+##### DASH Media Presentation Insertion (MPD alternate)
+
+It is not necessary to do anything, Shaka Player supports it natively without
+any type of intervention.
+
+
 ##### Custom Interstitials
 
 Example: