docs(vscode): Add VSCode/VSCodium installation instructions and refer…

…ence to Open VSX (#3244)

* docs: Add VSCode/VSCodium installation instructions and reference to Open VSX

Makes it obvious that VSCodium is also supported through Open VSX.

* [autofix.ci] apply automated fixes

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

clients/vscode/README.md

@@ -1,12 +1,20 @@
 # Tabby VSCode Extension
 
 [![License](https://img.shields.io/badge/License-Apache_2.0-blue.svg)](https://opensource.org/licenses/Apache-2.0)
-[![VSCode Extension Version](https://img.shields.io/visual-studio-marketplace/v/TabbyML.vscode-tabby)](https://marketplace.visualstudio.com/items?itemName=TabbyML.vscode-tabby)
-[![VSCode Extension Installs](https://img.shields.io/visual-studio-marketplace/i/TabbyML.vscode-tabby)](https://marketplace.visualstudio.com/items?itemName=TabbyML.vscode-tabby)
+[![Visual Studio Marketplace Extension Version](https://img.shields.io/visual-studio-marketplace/v/TabbyML.vscode-tabby?label=marketplace)](https://marketplace.visualstudio.com/items?itemName=TabbyML.vscode-tabby)
+[![Visual Studio Marketplace Extension Installs](https://img.shields.io/visual-studio-marketplace/i/TabbyML.vscode-tabby)](https://marketplace.visualstudio.com/items?itemName=TabbyML.vscode-tabby)
+[![Open VSX Extension Version](https://img.shields.io/open-vsx/v/TabbyML/vscode-tabby)](https://open-vsx.org/extension/TabbyML/vscode-tabby)
 [![Slack Community](https://shields.io/badge/Tabby-Join%20Slack-red?logo=slack)](https://links.tabbyml.com/join-slack)
 
 [Tabby](https://tabby.tabbyml.com/) is an open-source, self-hosted AI coding assistant designed to help you write code more efficiently.
 
+## Installation
+
+The Tabby extension can be installed from inside VisualStudio Code and VSCodium by copying the following command into the command palette (Ctrl+P):  
+`ext install TabbyML.vscode-tabby`
+
+It is also available for direct download on Open VSX: https://open-vsx.org/extension/TabbyML/vscode-tabby
+
 ## Autocomplete
 
 Tabby suggests multi-line code completions and full functions in real-time as you write code. Give it a try in the [online playground](https://tabby.tabbyml.com/playground).