Merge pull request #87 from boghyon/patch-1

"Upgrading": Remind readers of existing compatibility guidelines

docs/02_Read-Me-First/upgrading-9638e4f.md

@@ -2,5 +2,18 @@
 
 # Upgrading
 
-The following sections describe what you have to consider when upgrading to a new version of SAPUI5.
+Before upgrading to a newer SAPUI5 version, in general, you must first ensure that your development follows the documented compatibility guidelines strictly such as:
+
+-   **[Compatibility Rules](compatibility-rules-91f0873.md)**
+
+-   **[Use Only Public APIs](../03_Get-Started/use-only-public-apis-b0d5fe2.md)**
+
+-   **[Coding Issues to Avoid](../05_Developing_Apps/coding-issues-to-avoid-3877872.md)**
+
+-   **[The Owner Component](../04_Essentials/the-owner-component-a7a3138.md)**
+
+-   For SAPUI5 applications based on SAP Fiori elements: **[Read Before Extending a Generated App](../06_SAP_Fiori_Elements/read-before-extending-a-generated-app-d9c146a.md)**
+
+
+Afterwards, refer to the following version specific sections that describe what else you have to consider.