Improve iOS demo app readme (#5488)

Improve iOS demo app readme (#5453)

Summary:
Pull Request resolved: #5453

- Add instructions on how to clear package dependencies cache

Reviewed By: shoumikhin

Differential Revision: D62909056

fbshipit-source-id: ce5f595c9eebd51a7322209d562c98ff6c4c1c43
(cherry picked from commit 61e5d4c)

Co-authored-by: Riandy Riandy <riandymdn@meta.com>

examples/demo-apps/apple_ios/LLaMA/README.md

@@ -33,7 +33,8 @@ First it’s important to note that currently ExecuTorch provides support across
 ## How to Use the App
 This section will provide the main steps to use the app, along with a code snippet of the ExecuTorch API.
 
-```{note}
+### Swift Package Manager
+
 ExecuTorch runtime is distributed as a Swift package providing some .xcframework as prebuilt binary targets.
 Xcode will download and cache the package on the first run, which will take some time.
 
@@ -47,6 +48,13 @@ rm -rf \
   ~/Library/Developer/Xcode/DerivedData
 ```
 
+Link your binary with the ExecuTorch runtime and any backends or kernels used by the exported ML model. It is recommended to link the core runtime to the components that use ExecuTorch directly, and link kernels and backends against the main app target.
+
+Note: To access logs, link against the Debug build of the ExecuTorch runtime, i.e., the executorch_debug framework. For optimal performance, always link against the Release version of the deliverables (those without the _debug suffix), which have all logging overhead removed.
+
+For more details integrating and Running ExecuTorch on Apple Platforms, checkout this [link](https://pytorch.org/executorch/main/apple-runtime.html).
+
+### XCode
 * Open XCode and select "Open an existing project" to open `examples/demo-apps/apple_ios/LLama`.
 * Ensure that the ExecuTorch package dependencies are installed correctly, then select which ExecuTorch framework should link against which target.
 
@@ -61,7 +69,6 @@ rm -rf \
 * Run the app. This builds and launches the app on the phone.
 * In app UI pick a model and tokenizer to use, type a prompt and tap the arrow buton
 
-
 ## Copy the model to Simulator
 
 * Drag&drop the model and tokenizer files onto the Simulator window and save them somewhere inside the iLLaMA folder.

examples/demo-apps/apple_ios/LLaMA/docs/delegates/mps_README.md

@@ -39,10 +39,10 @@ Install dependencies
 ## Prepare Models
 In this demo app, we support text-only inference with Llama 3.1, Llama 3, and Llama 2 models.
 
-Install the required packages
+Install the required packages to export the model
 
 ```
-executorch/examples/models/llama2/install_requirements.sh
+sh examples/models/llama2/install_requirements.sh
 ```
 
 Export the model

examples/demo-apps/apple_ios/LLaMA/docs/delegates/xnnpack_README.md

@@ -39,10 +39,10 @@ Install dependencies
 ## Prepare Models
 In this demo app, we support text-only inference with up-to-date Llama models.
 
-Install the required packages
+Install the required packages to export the model
 
 ```
-executorch/examples/models/llama2/install_requirements.sh
+sh examples/models/llama2/install_requirements.sh
 ```
 
 Export the model