improved .env.example, added required env vars to deploy button

.env.example

@@ -1,2 +1,20 @@
+# Auto generated from Upstash integration (feel free to pull it from your Vercel project with `vc env pull`)
 UPSTASH_REDIS_REST_URL=
-UPSTASH_REDIS_REST_TOKEN=
+UPSTASH_REDIS_REST_TOKEN=
+
+# Required for email auth – setup instructions here: https://next-auth.js.org/providers/email#configuration
+EMAIL_SERVER=
+EMAIL_FROM=
+
+# Generate a random secret here: https://generate-secret.vercel.app/32
+NEXTAUTH_SECRET=
+
+# Required for adding domains to Vercel using the Domains API
+## Here's how you can get your Project & Team ID: https://github.com/vercel/vercel/discussions/4367#discussioncomment-1672222
+VERCEL_PROJECT_ID=
+VERCEL_TEAM_ID=
+## Here's how you can create an auth bearer token: https://vercel.com/guides/how-do-i-use-a-vercel-api-access-token#creating-an-access-token
+AUTH_BEARER_TOKEN=
+
+# Required for SQL database: you can follow this guide to set this up: https://vercel.com/guides/nextjs-multi-tenant-application#2.-set-up-your-mysql-database
+DATABASE_URL=

README.md

@@ -38,7 +38,7 @@ You can easily configure custom domains on Dub – just add an A/CNAME record t
 
 You can deploy your own hosted version of Dub for greater privacy & control. Just click the link below to deploy a ready-to-go version of Dub to Vercel.
 
-[![Deploy with Vercel](https://vercel.com/button)](https://vercel.com/new/clone?repository-url=https%3A%2F%2Fgithub.com%2Fsteven-tey%2Fdub&demo-title=Dub%20-%20Open-Source%20Link%20Shortener&demo-description=An%20open-source%20link%20shortener%20SaaS%20built%20with%20Vercel%20Edge%20Functions%20and%20Upstash.&project-name=Dub&repository-name=dub&demo-url=https%3A%2F%2Fdub.sh&demo-image=https%3A%2F%2Fdub.sh%2Fstatic%2Fthumbnail.png&integration-ids=oac_V3R1GIpkoJorr6fqyiwdhl17)
+[![Deploy with Vercel](https://vercel.com/button)](https://vercel.com/new/clone?repository-url=https%3A%2F%2Fgithub.com%2Fsteven-tey%2Fdub&demo-title=Dub%20-%20Open-Source%20Link%20Shortener&demo-description=An%20open-source%20link%20shortener%20SaaS%20built%20with%20Vercel%20Edge%20Functions%20and%20Upstash.&project-name=Dub&repository-name=dub&demo-url=https%3A%2F%2Fdub.sh&demo-image=https%3A%2F%2Fdub.sh%2Fstatic%2Fthumbnail.png&integration-ids=oac_V3R1GIpkoJorr6fqyiwdhl17&env=EMAIL_SERVER,EMAIL_FROM,NEXTAUTH_SECRET,VERCEL_PROJECT_ID,VERCEL_TEAM_ID,AUTH_BEARER_TOKEN,DATABASE_URL&envDescription=Follow%20the%20instructions%20here%20to%20set%20up%20the%20required%20env%20vars%3A&envLink=https%3A%2F%2Fgithub.com%2Fsteven-tey%2Fdub%2Fblob%2Fmain%2F.env.example))
 
 ## Tech Stack