minor #37962 Update Notifier bridge DSN in readme (jeremyFreeAgent)

This PR was merged into the 5.1 branch.

Discussion
----------

Update Notifier bridge DSN in readme

| Q             | A
| ------------- | ---
| Branch?       | 5.1
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Tickets       |
| License       | MIT
| Doc PR        |

Add missing DSN documentation in README for 5.1

Commits
-------

17c0784c44 Update Notifier bridge readme

src/Symfony/Component/Notifier/Bridge/Firebase/README.md

@@ -3,6 +3,18 @@ Firebase Notifier
 
 Provides Firebase integration for Symfony Notifier.
 
+DSN example
+-----------
+
+```
+// .env file
+FIREBASE_DSN=firebase://USERNAME:PASSWORD@default
+```
+
+where:
+ - `USERNAME` is your Firebase username
+ - `PASSWORD` is your Firebase password
+
 Resources
 ---------
 

src/Symfony/Component/Notifier/Bridge/Mattermost/README.md

@@ -3,6 +3,18 @@ Mattermost Notifier
 
 Provides Mattermost integration for Symfony Notifier.
 
+DSN example
+-----------
+
+```
+// .env file
+MATTERMOST_DSN=mattermost://ACCESS_TOKEN@default?channel=CHANNEL
+```
+
+where:
+ - `ACCESS_TOKEN` is your Mattermost access token
+ - `CHANNEL` is your Mattermost channel
+
 Resources
 ---------
 

src/Symfony/Component/Notifier/Bridge/RocketChat/README.md

@@ -3,6 +3,18 @@ RocketChat Notifier
 
 Provides RocketChat integration for Symfony Notifier.
 
+DSN example
+-----------
+
+```
+// .env file
+ROCKETCHAT_DSN=rocketchat://ACCESS_TOKEN@default?channel=CHANNEL
+```
+
+where:
+ - `ACCESS_TOKEN` is your RocketChat access token
+ - `CHANNEL` is your RocketChat channel
+
 Resources
 ---------
 

src/Symfony/Component/Notifier/Bridge/Sinch/README.md

@@ -3,6 +3,19 @@ Sinch Notifier
 
 Provides Sinch integration for Symfony Notifier.
 
+DSN example
+-----------
+
+```
+// .env file
+SINCH_DSN=sinch://SERVICE_PLAN_ID:AUTH_TOKEN@default?from=FROM
+```
+
+where:
+ - `SERVICE_PLAN_ID` is your Sinch service plan id
+ - `AUTH_TOKEN` is your Sinch auth token
+ - `FROM` is your sender
+
 Resources
 ---------