docs: Update README templates to include instructions for generating embeddings

templates/types/simple/express/README-template.md

@@ -8,7 +8,13 @@ First, install the dependencies:
 npm install
 ```
 
-Second, run the development server:
+Second, generate the embeddings of the documents in the `./data` directory (if this folder exists - otherwise, skip this step):
+
+```
+npm run generate
+```
+
+Third, run the development server:
 
 ```
 npm run dev

templates/types/streaming/express/README-template.md

@@ -8,7 +8,13 @@ First, install the dependencies:
 npm install
 ```
 
-Second, run the development server:
+Second, generate the embeddings of the documents in the `./data` directory (if this folder exists - otherwise, skip this step):
+
+```
+npm run generate
+```
+
+Third, run the development server:
 
 ```
 npm run dev

templates/types/streaming/nextjs/README-template.md

@@ -8,7 +8,13 @@ First, install the dependencies:
 npm install
 ```
 
-Second, run the development server:
+Second, generate the embeddings of the documents in the `./data` directory (if this folder exists - otherwise, skip this step):
+
+```
+npm run generate
+```
+
+Third, run the development server:
 
 ```
 npm run dev