Adds supabase as the issuer for the JWT token

web/docs/learn/auth-deep-dive/jwts.md

@@ -122,6 +122,7 @@ If we put this token into https://jwt.io, we see it decodes to:
 ```js
 {
   "role": "anon",
+  "iss": "supabase",
   "iat": 1614205174,
   "exp": 1929781174
 }

web/src/components/JwtGenerator.js

@@ -9,6 +9,7 @@ const fiveYears = new Date(now.getFullYear() + 5, now.getMonth(), now.getDate())
 const anonToken = `
 {  
     "role": "anon",
+    "iss": "supabase",
     "iat": ${Math.floor(today / 1000)},
     "exp": ${Math.floor(fiveYears / 1000)}
 }
@@ -17,6 +18,7 @@ const anonToken = `
 const serviceToken = `
 {  
     "role": "service_role",
+    "iss": "supabase",
     "iat": ${Math.floor(today / 1000)},
     "exp": ${Math.floor(fiveYears / 1000)}
 }