docs: use Tabs for manual guide and restore H3 steps

pages/guide/getting-started/install-root-ca.mdx

@@ -57,8 +57,8 @@ import { Steps } from 'nextra/components'
 
 If you prefer to install certificates manually, follow these steps for your operating system.
 
-### Windows
-
+<Tabs items={['Windows', 'macOS', 'Android']}>
+  <Tabs.Tab>
     <Steps>
       ### Download the Certificate
       Download the **[Root CA (.crt)](https://cdn.trustlab.dyzulk.com/ca/dydev-its-true.crt)** file.
@@ -76,9 +76,8 @@ Select **Trusted Root Certification Authorities**.
       ### Finish
       Click Next and Finish. The certificate is now installed system-wide.
     </Steps>
-
-### macOS
-
+  </Tabs.Tab>
+  <Tabs.Tab>
     <Steps>
       ### Download
       Download the **[Root CA (.crt)](https://cdn.trustlab.dyzulk.com/ca/dydev-its-true.crt)** file.
@@ -92,9 +91,8 @@ Double-click the "DyDev Its True" (Root CA) in the list.
       Expand the **Trust** section.
       Change "When using this certificate" to **Always Trust**.
     </Steps>
-
-### Android
-
+  </Tabs.Tab>
+  <Tabs.Tab>
     <Steps>
       ### Download
       Download the **[Root CA (.crt)](https://cdn.trustlab.dyzulk.com/ca/dydev-its-true.crt)** or **[DER Format](https://cdn.trustlab.dyzulk.com/ca/dydev-its-true.der)**.
@@ -106,4 +104,6 @@ Tap **Install a certificate** > **CA Certificate**.
       ### Select File
       Select "Install anyway" if prompted, then choose the downloaded file.
     </Steps>
+  </Tabs.Tab>
+</Tabs>