fix: fix language switch and provide further documentation (#46)

Adoc documentation has been slightly improved. 
Reference implementation for language switch has been fixed.
[Documentation](https://github.com/e-Spirit/fsxa-pwa/blob/master/docs/modules/ROOT/pages/components/FSXABaseComponent.adoc) for the language switch hase been added.

components/fsxa/AppLayout.tsx

@@ -93,7 +93,6 @@ class AppLayout extends FSXABaseAppLayout {
   handleNavigationClick(item: NavigationItem) {
     if (['language.de', 'language.en'].includes(item.key as string)) {
       this.triggerRouteChange({
-        pageId: this.currentPage?.id,
         locale: item.key === 'language.de' ? 'de_DE' : 'en_GB'
       })
     } else {

docs/modules/ROOT/pages/components/FSXABaseComponent.adoc

@@ -8,7 +8,8 @@
 == Introduction
 
 The FSXABaseComponent is there to have a basic component to be able to implement further components.
-It provides different attributes and methods, which should simplify the development significantly. These are described in this section.
+It provides different attributes and methods, which should simplify the development significantly. 
+These are described in this section.
 
 == Usage
 
@@ -52,19 +53,22 @@ Note: If you only want type support for your slots and not the props or events y
 
 === `currentPage` - string
 
-This property returns the NavigationItem that is matching the current path. If `null` is returned, no current route could be matched to the current path.
+This property returns the NavigationItem that is matching the current path. 
+If `null` is returned, no current route could be matched to the current path.
 
 === `fsxaApi` - Object
 
 This property returns a preconfigured and ready-to-use FSXA-API instance.
 
 === `globalSettings` - string
 
-This property returns the globally configured project properties. If no projectProperties are defined in your CaaS this will return `null`.
+This property returns the globally configured project properties. 
+If no projectProperties are defined in your CaaS this will return `null`.
 
 === `isEditMode` - boolean
 
-This property returns `true` if the app is delivering preview data. It will return `false` if it is released data.
+This property returns `true` if the app is delivering preview data.
+It will return `false` if it is released data.
 
 === `locale` - string
 
@@ -92,7 +96,8 @@ This method returns the stored data which was set with the given key.
 getUrlByPageId(pageId: string, locale?: string | undefined): string | null
 ----
 
-This method returns the corresponding route for a given `pageId`. If no page was found `null` will be returned.
+This method returns the corresponding route for a given `pageId`.
+If no page was found `null` will be returned.
 
 === `setStoredItem`
 
@@ -113,4 +118,22 @@ You can specify a time-to-live duration in ms, that determines how long the valu
 triggerRouteChange(params: {pageId?:string, route?:string, locale?:string}): Promise<void>
 ----
 
-This method will trigger a route change request. A `pageId`, `route` or `locale` can be passed in. If a corresponding page is found the route change will be triggered. Since this is only available when javascript is enabled, make sure that some kind of fallback is provided.
+This method will trigger a route change request. A `pageId`, `route` or `locale` can be passed in. 
+If a corresponding page is found the route change will be triggered. 
+Since this is only available when javascript is enabled, make sure that some kind of fallback is provided.
+
+==== `language switch`
+
+With the `triggerRouteChange` method you can also implement a language switch.
+When implementing this you have to provide a valid locale abbreviation. 
+Make sure that you *only* pass the locale parameter.
+Otherwise, undesirable side effects may occur.
+
+
+Example:
+[source, javascript]
+----
+triggerRouteChange({locale: 'en_GB'})
+----
+
+