Add introductions to base image subsections and move note to end

Author: dobrac

docs/template/base-image.mdx

@@ -29,12 +29,12 @@ template = Template(
 
 ## Defining base image
 
-<Note>
-You can only call base image methods once per template. Subsequent calls will throw an error.
-</Note>
+Every template starts with a base image that provides the foundation for your sandbox environment.
 
 ### Predefined base images
 
+Use convenience methods for common base images with Ubuntu, Debian, Python, Node.js, or Bun:
+
 <CodeGroup>
 
 ```typescript JavaScript & TypeScript
@@ -57,6 +57,8 @@ template.from_bun_image("1.3")  # oven/bun:1.3
 
 ### Custom base image
 
+Use any Docker image from Docker Hub or other registries:
+
 <CodeGroup>
 
 ```typescript JavaScript & TypeScript
@@ -71,6 +73,8 @@ template.from_image("custom-image:latest")
 
 ### Default E2B base image
 
+Use the default E2B base image, which comes pre-configured for sandbox environments:
+
 <CodeGroup>
 
 ```typescript JavaScript & TypeScript
@@ -85,6 +89,8 @@ template.from_base_image()  # e2bdev/base
 
 ### Build from existing template
 
+Extend an existing template from your team or organization:
+
 <CodeGroup>
 
 ```typescript JavaScript & TypeScript
@@ -99,6 +105,10 @@ template.from_template("acme/other-template")  # Full namespaced reference
 
 </CodeGroup>
 
+<Note>
+You can only call base image methods once per template. Subsequent calls will throw an error.
+</Note>
+
 ## Parsing existing Dockerfiles
 
 Convert existing Dockerfiles to template format using `fromDockerfile()`: