update installation guide on examples (#78)

Author: badmonster0

examples/code_embedding/README.md

@@ -1,7 +1,7 @@
 Simple example for cocoindex: build embedding index based on local files.
 
 ## Prerequisite
-Follow [Setup Postgres](../../#setup-postgres) section on the root directory to setup Postgres database.
+[Install Postgres](https://cocoindex.io/docs/getting_started/installation#-install-postgres) if you don't have one.
 
 ## Run
 
@@ -36,4 +36,4 @@ Run CocoInsight to understand your RAG data pipeline:
 
 ```
 python code_embedding.py cocoindex server -c https://cocoindex.io/cocoinsight
-```
+```

examples/manual_extraction/README.md

@@ -1,7 +1,7 @@
 Simple example for cocoindex: extract structured information from a Markdown file.
 
 ## Prerequisite
-Follow [Setup Postgres](../../#setup-postgres) section on the root directory to setup Postgres database.
+[Install Postgres](https://cocoindex.io/docs/getting_started/installation#-install-postgres) if you don't have one.
 
 ## Run
 

examples/pdf_embedding/README.md

@@ -1,7 +1,7 @@
 Simple example for cocoindex: build embedding index based on local files.
 
 ## Prerequisite
-Follow [Setup Postgres](../../#setup-postgres) section on the root directory to setup Postgres database.
+[Install Postgres](https://cocoindex.io/docs/getting_started/installation#-install-postgres) if you don't have one.
 
 ## Run
 
@@ -36,4 +36,4 @@ Run CocoInsight to understand your RAG data pipeline:
 
 ```
 python pdf_embedding.py cocoindex server -c https://cocoindex.io/cocoinsight
-```
+```

examples/text_embedding/README.md

@@ -1,7 +1,7 @@
 Simple example for cocoindex: build embedding index based on local files.
 
 ## Prerequisite
-Follow [Setup Postgres](../../#setup-postgres) section on the root directory to setup Postgres database.
+[Install Postgres](https://cocoindex.io/docs/getting_started/installation#-install-postgres) if you don't have one.
 
 ## Run
 
@@ -36,4 +36,4 @@ Run CocoInsight to understand your RAG data pipeline:
 
 ```
 python text_embedding.py cocoindex server -c https://cocoindex.io/cocoinsight
-```
+```