Update bluegreen.md

Author: bcb

docs/bluegreen.md

@@ -33,15 +33,15 @@ caddy:
   container_name: ${STACK_NAME}_caddy
 ```
 
-## Postgres
+## 2. Postgres
 
 Running two separate PostgreSQL instances and having them both simultaneously
 access the same data directory within that shared volume is not recommended and
 can lead to data corruption.
 
 So we need to move Postgres out of the compose file and start it separately.
 
-### Share volumes between the stacks
+## 3. Volumes
 
 To share data between the two stacks (uploads, etc.), give volumes explicit
 names:
@@ -52,7 +52,7 @@ volumes:
     name: user-data
 ```
 
-## 3. Bring up two Stacks
+## 4. Bring up two Stacks
 
 Deploying is the same as [before](deploying.md), but now we're deploying the
 _idle stack_. For this example, `green` is idle so that's the one we're
@@ -76,7 +76,7 @@ docker compose up -d
 Docker will use the directory name `green` as the project name, creating
 different containers, volumes and networks than the `blue` stack.
 
-## 3. Add a Front Proxy
+## 5. Add a Front Proxy
 
 The _front proxy_ is a single container that binds ports `80` and `443` on the
 server and routes requests into either the Blue or Green stack.
@@ -111,7 +111,7 @@ docker run -d \
   caddy:2
 ```
 
-## 4. Upgrading
+## 6. Upgrading
 
 ## Flip traffic