Move installation requirements to the header

Author: icinga-migration

doc/02-Installation.md

@@ -4,46 +4,24 @@
 The preferred way of installing Icinga Web 2 is to use the official package repositories depending on which operating
 system and distribution you are running.
 
+Before installing Icinga Web 2, make sure you have installed [Icinga 2](https://icinga.com/docs/icinga-2) 
+and [Icinga DB](https://icinga.com/docs/icinga-db), to monitor your infrastructure.
+ Also a web server (e.g. Apache or Nginx) and PHP version ≥ 8.2 are required to be installed.
+
+Optionally, the [pdfexport](https://github.com/Icinga/icingaweb2-module-pdfexport) module (≥0.13.0) to export the PDF 
+and LDAP PHP library when using Active Directory or LDAP for authentication are required.
+
 Please follow the steps listed for your operating system. Packages for distributions other than the ones
 listed here may also be available. Please refer to [icinga.com/get-started/download](https://icinga.com/get-started/download/#community)
 for a full list of available community repositories.
 
-## Browser Support
-
-Icinga Web 2 and modules made by Icinga don't require a particular browser or set of browsers. The
-vendor of the browser in question doesn't matter much. However, the features a browser supports do.
-
-This generally applies to CSS and Javascript features. Since there a plethora of features in each
-category which Icinga Web 2 and modules may require, we will only mention the most prominent feature
-or sub-category here:
-
-* For CSS this is [the flexible box layout module](https://caniuse.com/flexbox)
-* For Javascript it is [the ECMAScript 2015 specification](https://caniuse.com/es6)
-
-If your desired browser and its version is showing up in green when visiting the respective link,
-it's probably okay to use it for Icinga Web 2.
-
 ## Upgrade <a id="upgrade"></a>
 
 In case you are upgrading from an older version of Icinga Web 2
 please make sure to read the [upgrading](80-Upgrading.md#upgrading) section
 thoroughly.
 <!-- {% elif not from_source %} -->
 
-## Installation Requirements <a id="installation-requirements"></a>
-
-* [Icinga 2](https://icinga.com/docs/icinga-2) and [Icinga DB](https://icinga.com/docs/icinga-db) to
-  monitor your infrastructure
-* A web server, e.g. Apache or Nginx
-* PHP version ≥ 8.2
-* MariaDB
-
-### Optional Requirements
-
-* The [pdfexport](https://github.com/Icinga/icingaweb2-module-pdfexport) module (≥0.13.0) is required for the
-  export to PDF
-* LDAP PHP library when using Active Directory or LDAP for authentication
-
 ## Installing the Web Server <a id="install-the-web-server"></a>
 
 Ensure that you have a web server with PHP installed before proceeding,
@@ -75,7 +53,7 @@ icingacli setup token show
 
 <!-- {% if debian or ubuntu %} -->
 You need to manually create a database and a database user prior to starting the web wizard.
-This is due to local security restrictions whereas the web wizard cannot create a database/user through
+This is due to local security restrictions, whereas the web wizard cannot create a database/user through
 a local unix domain socket.
 
 ```bash