[Improvement] customize add method (#988)

docs/data-sources/custom.mdx

@@ -0,0 +1,41 @@
+---
+title: '⚙️ Custom'
+---
+
+When we say "custom", we mean that you can customize the loader and chunker to your needs. This is done by passing a custom loader and chunker to the `add` method.
+
+```python
+from embedchain import Pipeline as App
+import your_loader
+import your_chunker
+
+app = App()
+loader = your_loader()
+chunker = your_chunker()
+
+app.add("source", data_type="custom", loader=loader, chunker=chunker)
+```
+
+<Note>
+    The custom loader and chunker must be a class that inherits from the [`BaseLoader`](https://github.com/embedchain/embedchain/blob/main/embedchain/loaders/base_loader.py) and [`BaseChunker`](https://github.com/embedchain/embedchain/blob/main/embedchain/chunkers/base_chunker.py) classes respectively.
+</Note>
+
+<Note>
+    If the `data_type` is not a valid data type, the `add` method will fallback to the `custom` data type and expect a custom loader and chunker to be passed by the user.
+</Note>
+
+Example:
+
+```python
+from embedchain import Pipeline as App
+from embedchain.loaders.github import GithubLoader
+
+app = App()
+
+loader = GithubLoader(config={"token": "ghp_xxx"})
+
+app.add("repo:embedchain/embedchain type:repo", data_type="github", loader=loader)
+
+app.query("What is Embedchain?")
+# Answer: Embedchain is a Data Platform for Large Language Models (LLMs). It allows users to seamlessly load, index, retrieve, and sync unstructured data in order to build dynamic, LLM-powered applications. There is also a JavaScript implementation called embedchain-js available on GitHub.
+```

docs/data-sources/overview.mdx

@@ -26,6 +26,7 @@ Embedchain comes with built-in support for various data sources. We handle the c
   <Card title="🗨️ Discourse" href="/data-sources/discourse"></Card>
   <Card title="💬 Discord" href="/data-sources/discord"></Card>
   <Card title="📝 Github" href="/data-sources/github"></Card>
+  <Card title="⚙️ Custom" href="/data-sources/custom"></Card>
 </CardGroup>
 
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