docs: add target Blockly version note to all codelabs

packages/docs/docs/codelabs/context-menu-option/setup.mdx

@@ -35,3 +35,5 @@ const storageKey = 'contextMenuWorkspace';
 Take a moment to explore the code you just created in the `context-menu-option-codelab` folder. If you'd like a more in-depth explanation of all of the code in the sample app, check out the [getting started codelab](/codelabs/getting-started/codelab-overview) which goes through creating this sample app from scratch.
 
 For a briefer outline of the code, visit the [sample app overview](/guides/get-started/sample-app-overview/) page for an overview of the included files and tooling.
+
+> **Note:** This codelab is targeted for Blockly v13.

packages/docs/docs/codelabs/css/setup.mdx

@@ -48,3 +48,5 @@ The pieces that matter most for this codelab are:
 
 - `src/toolbox.js` - defines the toolbox's categories. You'll add a CSS class to each category so you can target it with a CSS rule.
 - `src/index.js` - injects the workspace. You'll import your new stylesheet here.
+
+> **Note:** This codelab is targeted for Blockly v13.

packages/docs/docs/codelabs/custom-generator/setup.mdx

@@ -176,3 +176,5 @@ If the server is already running, refresh the page to see changes. Otherwise, ru
 />
 
 The app is still trying to generate and run JavaScript for the workspace, instead of JSON. The next section changes that.
+
+> **Note:** This codelab is targeted for Blockly v13.

packages/docs/docs/codelabs/custom-mutator/setup.mdx

@@ -35,3 +35,5 @@ const storageKey = 'customMutatorWorkspace';
 Take a moment to explore the code you just created in the `custom-mutator-codelab` folder. If you'd like a more in-depth explanation of all of the code in the sample app, check out the [getting started codelab](/codelabs/getting-started/codelab-overview) which goes through creating this sample app from scratch.
 
 For a briefer outline of the code, visit the [sample app overview](/guides/get-started/sample-app-overview/) page for an overview of the included files and tooling.
+
+> **Note:** This codelab is targeted for Blockly v13.

packages/docs/docs/codelabs/custom-renderer/setup.mdx

@@ -35,3 +35,5 @@ const storageKey = 'customRendererWorkspace';
 Take a moment to explore the code you just created in the `custom-renderer-codelab` folder. If you'd like a more in-depth explanation of all of the code in the sample app, check out the [getting started codelab](/codelabs/getting-started/codelab-overview) which goes through creating this sample app from scratch.
 
 For a briefer outline of the code, visit the [sample app overview](/guides/get-started/sample-app-overview/) page for an overview of the included files and tooling.
+
+> **Note:** This codelab is targeted for Blockly v13.

packages/docs/docs/codelabs/custom-toolbox/setup.mdx

@@ -39,3 +39,5 @@ const storageKey = 'customToolboxWorkspace';
 Take a moment to explore the code you just created in the `custom-toolbox-codelab` folder. If you'd like a more in-depth explanation of all of the code in the sample app, check out the [getting started codelab](/codelabs/getting-started/codelab-overview) which goes through creating this sample app from scratch.  
 
 For a briefer outline of the code, visit the [sample app overview](/guides/get-started/sample-app-overview/) page for an overview of the included files and tooling. 
+
+> **Note:** This codelab is targeted for Blockly v13.

packages/docs/docs/codelabs/getting-started/setup.mdx

@@ -32,3 +32,4 @@ The starter code folder contains:
 - `package.json`: Stores basic information about the app. 
 - `webpack.config.js`: The configuration for webpack, which handles the application bundling and running the server.
 
+> **Note:** This codelab is targeted for Blockly v13.

packages/docs/docs/codelabs/theme-extension-identifier/setup.mdx

@@ -47,3 +47,5 @@ Open the window with your running app. You should see a Blockly workspace with a
   alt="The Blockly sample app with a default-themed workspace and toolbox."
   className="codelabImage"
 />
+
+> **Note:** This codelab is targeted for Blockly v13.

packages/docs/docs/codelabs/validation-and-warnings/setup.mdx

@@ -41,3 +41,5 @@ The pieces that matter most for this codelab are:
 - `src/generators/javascript.js` - defines how to generate JavaScript code from the custom blocks.
 - `src/toolbox.js` - defines which blocks are available in the toolbox.
 - `src/index.js` - registers the blocks and generators, injects the workspace, and re-runs the generated code whenever the workspace changes.
+
+> **Note:** This codelab is targeted for Blockly v13.

packages/docs/docs/guides/contribute/docs/write_a_codelab.mdx

@@ -69,6 +69,8 @@ writing a codelab.
   explain its code.
 - What is the minimum setup required for the user to run your code?
 
+New codelabs should state the version of Blockly they are written for.
+
 ### Structure
 
 As with any writing, start with an outline. This is a good structure for most