Use new syntax in post install

POSTINSTALL.md

@@ -1,12 +1,19 @@
-This installation does not come with any pre-setup users. Create new users in the registration form of the app.
+<nosso>
 
-Taiga does not come with any global admin panel, every user creating a new project is the admin of that project.
+This installation does not come with any pre-setup users. Create new users
+in the registration form of the app.
 
-=== sso ===
+</nosso>
 
-This app integrates with Cloudron authentication, however **before** adding Cloudron users to projects in Taiga,
-they have to login into the app once, otherwise the app assumes this is an external user and will send an invite.
+<sso>
+This app integrates with Cloudron authentication. However **before** adding
+Cloudron users to projects in Taiga, they have to login into the app once.
+Otherwise the app assumes this is an external user and will send an invite.
 
-Taiga does not come with any global admin panel, every user creating a new project is the admin of that project.
+Public registration is disabled. If required, please install an instance of
+Taiga without Cloudron user integration.
+</sso>
+
+Note that Taiga does not have a global admin panel, every user creating a
+new project is the admin of that project.
 
-The public registration is disabled, if required, please install an instance of Taiga without Cloudron user integration.