fix some dangling corp playground links

Author: erikhatcher

docs/40_Analysis/5_custom.mdx

@@ -15,20 +15,19 @@ Composed from analyzer building blocks:
 ## Custom analyzers
 
 ### last 4 digits
-Last 4 digit of phone number matching (regex extraction during indexing, keyword analysis at query time): https://search-playground.corp.mongodb.com/tools/code-playground/snapshots/669e6c98d49ef6fad98118ba
+ <Playground url="https://search-playground.corp.mongodb.com/tools/code-playground/snapshots/669e6c98d49ef6fad98118ba">🔗 Last 4 digit of phone number matching</Playground> (regex extraction during indexing, keyword analysis at query time)
 
 ### reverse token filter
-Example of being able to do ‘startsWith’ and ‘endsWith’ using wildcard and ‘reverse’ token filter:
-https://search-playground.mongodb.com/tools/code-playground/snapshots/6683c8bc4a45448733549bbc
+<Playground url="https://search-playground.mongodb.com/tools/code-playground/snapshots/6683c8bc4a45448733549bbc">🔗 Example of being able to do ‘startsWith’ and ‘endsWith’ using wildcard and ‘reverse’ token filter</Playground>
 
 ### starts-with
-Example of being able to do ‘startsWith’, ‘endsWith’ and ‘contains’ using nGrams: https://search-playground.mongodb.com/tools/code-playground/snapshots/6683c999934a05d9b585b6e7 
+<Playground url="https://search-playground.mongodb.com/tools/code-playground/snapshots/6683c999934a05d9b585b6e7">🔗 Example of being able to do ‘startsWith’, ‘endsWith’ and ‘contains’ using nGrams</Playground>
 
 ## Exercises
 
 ### HTML stripping indexer on English text
 
-https://search-playground.corp.mongodb.com/tools/code-sandbox/snapshots/6796a293aa132ffc76719f61
+<Playground url="https://search-playground.corp.mongodb.com/tools/code-sandbox/snapshots/6796a293aa132ffc76719f61">🔗 Stripping HTML tags for indexing</Playground>
 
 From there:
   * `lucene.english` - "span" and "alert" are indexed/searchable

docs/40_Analysis/9_advanced.mdx

@@ -1,8 +1,7 @@
 # 🦹 Advanced
 
 ## Synonyms
-
-TODO: get this working: https://search-playground.corp.mongodb.com/tools/code-sandbox/snapshots/67b588c6828ad15116bccda5
+<Playground url="https://search-playground.corp.mongodb.com/tools/code-sandbox/snapshots/67b588c6828ad15116bccda5">🔗 TODO: synonyms</Playground>
 
   * st/street, rd/road