Revise linode-cli installation instructions

Updated installation instructions for linode-cli to recommend using pipx for better isolation and compatibility.

Author: zliang-akamai

README.md

@@ -12,16 +12,21 @@ Visit the [Wiki](../../wiki) for more information.
 
 ## Install
 
-Install via PyPI:
+We recommend installing `linode-cli` with `pipx`, which installs each Python CLI tool into its own isolated environment and works on distributions where `pip install` fails because the system Python is marked as externally managed ([PEP 668](https://peps.python.org/pep-0668/)). If pipx isn't installed yet, follow the [pipx installation guide](https://pipx.pypa.io/latest/how-to/install-pipx.html).
+
+To install:
+
 ```bash
 pipx install linode-cli
 ```
+
 To upgrade:
-```
+
+```bash
 pipx upgrade linode-cli
 ```
-We recommend using `pipx` to install `linode-cli`, as it installs Python CLI tools in isolated environments and avoids conflicts with system-managed Python packages (PEP 668).
-Visit the [Wiki](../../wiki/Installation) for more information.
+
+The [Wiki](https://github.com/linode/linode-cli/wiki/Installation) covers other installation methods, including the Docker image, the GitHub Action, and building from source.
 
 ## Contributing