Small clarifications. (#624)

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## Description
Small clarifications in README.md.

## DCO Affirmation
I affirm that all code in every commit of this pull request conforms to
the terms of the Topoteretes Developer Certificate of Origin


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **Documentation**
- Updated documentation to feature a single, centrally positioned demo
link for clearer navigation.
- Clarified setup instructions to indicate that default configurations
are applied when custom environment variables are not provided.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

README.md

@@ -8,11 +8,11 @@
   cognee - memory layer for AI apps and Agents
 
   <p align="center">
+  <a href="https://www.youtube.com/watch?v=1bezuvLwJmw&t=2s">Demo</a>
+  .
   <a href="https://cognee.ai">Learn more</a>
   ·
   <a href="https://discord.gg/NQPKmU5CCg">Join Discord</a>
-  ·
-  <a href="https://www.youtube.com/watch?v=1bezuvLwJmw&t=2s">Demo</a>
   </p>
 
 
@@ -89,7 +89,7 @@ Add LLM_API_KEY to .env using the command bellow.
 ```
 echo "LLM_API_KEY=YOUR_OPENAI_API_KEY" > .env
 ```
-You can see available env variables in the repository `.env.template` file.
+You can see available env variables in the repository `.env.template` file. If you don't specify it otherwise, like in this example, SQLite (relational database), LanceDB (vector database) and NetworkX (graph store) will be used as default components.
 
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