fix: add prompt to example in messages

messages/accesstoken.store.json

@@ -1,8 +1,8 @@
 {
   "description": "authorize an org using an existing Salesforce access token\nBy default, the command runs interactively and asks you for the access token. If you previously authorized the org, the command prompts whether you want to overwrite the local file. Specify --noprompt to not be prompted.\nTo use the command in a CI/CD script, set the SFDX_ACCESS_TOKEN environment variable to the access token. Then run the command with the --noprompt parameter.",
   "examples": [
-    "sfdx auth:accesstoken:store --instanceurl https://mycompany.my.salesforce.com",
-    "export SFDX_ACCESS_TOKEN=00Dxx0000000000!xxxxx\nsfdx auth:accesstoken:store --instanceurl https://dev-hub.my.salesforce.com --noprompt"
+    "$ sfdx auth:accesstoken:store --instanceurl https://mycompany.my.salesforce.com",
+    "$ export SFDX_ACCESS_TOKEN=00Dxx0000000000!xxxxx\nsfdx auth:accesstoken:store --instanceurl https://dev-hub.my.salesforce.com --noprompt"
   ],
   "invalidAccessTokenFormat": "The access token isn't in the correct format.\nIt should follow this pattern: %s."
 }