Convert Calendars page to HTML admonitions (#2388)

Signed-off-by: Daniel Gray <dngray@privacyguides.org>

docs/calendar.md

@@ -8,7 +8,7 @@ Calendars contain some of your most sensitive data; use products that implement
 
 ## Tuta
 
-!!! recommendation
+<div class="admonition recommendation" markdown>
 
 ![Tuta logo](assets/img/calendar/tuta.svg){ align=right }
 
@@ -22,7 +22,8 @@ Calendars contain some of your most sensitive data; use products that implement
 [:octicons-code-16:](https://github.com/tutao/tutanota){ .card-link title="Source Code" }
 [:octicons-heart-16:](https://tuta.com/community/){ .card-link title=Contribute }
 
-    ??? downloads
+<details class="downloads" markdown>
+<summary>Downloads</summary>
 
 - [:simple-googleplay: Google Play](https://play.google.com/store/apps/details?id=de.tutao.tutanota)
 - [:simple-appstore: App Store](https://apps.apple.com/us/app/tutanota/id922429609)
@@ -32,9 +33,13 @@ Calendars contain some of your most sensitive data; use products that implement
 - [:simple-flathub: Flathub](https://flathub.org/apps/com.tutanota.Tutanota)
 - [:octicons-browser-16: Web](https://app.tuta.com/)
 
+</details>
+
+</div>
+
 ## Proton Calendar
 
-!!! recommendation
+<div class="admonition recommendation" markdown>
 
 ![Proton](assets/img/calendar/proton-calendar.svg){ align=right }
 
@@ -45,22 +50,30 @@ Calendars contain some of your most sensitive data; use products that implement
 [:octicons-info-16:](https://proton.me/support/proton-calendar-guide){ .card-link title=Documentation}
 [:octicons-code-16:](https://github.com/ProtonMail/WebClients){ .card-link title="Source Code" }
 
-    ??? downloads
+<details class="downloads" markdown>
+<summary>Downloads</summary>
 
 - [:simple-googleplay: Google Play](https://play.google.com/store/apps/details?id=me.proton.android.calendar)
 - [:simple-appstore: App Store](https://apps.apple.com/app/apple-store/id1514709943)
 - [:octicons-browser-16: Web](https://calendar.proton.me)
 
+</details>
+
+</div>
+
 Unfortunately, as of January 2024 Proton has [still](https://discuss.privacyguides.net/t/proton-calendar-is-not-open-source-mobile/14656/8) not released the source code for their mobile Calendar app on Android or iOS. Proton Calendar's web client is open source.
 
 ## Criteria
 
 **Please note we are not affiliated with any of the projects we recommend.** In addition to [our standard criteria](about/criteria.md), we have developed a clear set of requirements to allow us to provide objective recommendations. We suggest you familiarize yourself with this list before choosing to use a project, and conduct your own research to ensure it's the right choice for you.
 
-!!! example "This section is new"
+<div class="admonition example" markdown>
+<p class="admonition-title">This section is new</p>
 
 We are working on establishing defined criteria for every section of our site, and this may be subject to change. If you have any questions about our criteria, please [ask on our forum](https://discuss.privacyguides.net/latest) and don't assume we didn't consider something when making our recommendations if it is not listed here. There are many factors considered and discussed when we recommend a project, and documenting every single one is a work-in-progress.
 
+</div>
+
 ### Minimum Qualifications
 
 - Must sync and store information with E2EE to ensure data is not visible to the service provider.