(AzureCXP)MicrosoftDocs/azure-docs/issues/51493

updated connection strings prefixed connection types  as below, also added Azure Databases for PostgreSQL which is an option now, seen from Azure Portal and added the connection string prefix for that is "POSTGRESQLCONNSTR_" which isn't documented here.
* SQLServer: `SQLCONNSTR_`  
* SQLAzure: `SQLAZURECONNSTR_` 
* PostgreSQL: `POSTGRESQLCONNSTR_`

Author: SnehaAgrawal-MSFT

articles/app-service/configure-common.md

@@ -91,10 +91,11 @@ For other language stacks, it's better to use [app settings](#configure-app-sett
 
 At runtime, connection strings are available as environment variables, prefixed with the following connection types:
 
-* SQL Server: `SQLCONNSTR_`
-* MySQL: `MYSQLCONNSTR_`
-* SQL Database: `SQLAZURECONNSTR_`
+* SQLServer: `SQLCONNSTR_`  
+* MySQL: `MYSQLCONNSTR_` 
+* SQLAzure: `SQLAZURECONNSTR_` 
 * Custom: `CUSTOMCONNSTR_`
+* PostgreSQL: `POSTGRESQLCONNSTR_`  
 
 For example, a MySql connection string named *connectionstring1* can be accessed as the environment variable `MYSQLCONNSTR_connectionString1`. For language-stack specific steps, see: