docs(installing): add pnpm (#22823)

Co-authored-by: Charis <26616127+charislam@users.noreply.github.com>

apps/docs/docs/ref/javascript/installing.mdx

@@ -36,6 +36,13 @@ custom_edit_url: https://github.com/supabase/supabase/edit/master/web/spec/supab
         ```
 
       </TabPanel>
+      <TabPanel id="pnpm" label="pnpm">
+
+        ```sh Terminal
+        pnpm add @supabase/supabase-js
+        ```
+
+      </TabPanel>
     </Tabs>
 
   </RefSubLayout.Examples>