feat: add customUnWelcomePage macro for nsis (#7790)

Author: xianyunleo

.changeset/real-planets-float.md

@@ -0,0 +1,5 @@
+---
+"app-builder-lib": minor
+---
+
+feat: add customUnWelcomePage macro for NSIS installers

docs/configuration/nsis.md

@@ -37,7 +37,7 @@ Two options are available — [include](#NsisOptions-include) and [script](#Nsis
 Keep in mind — if you customize NSIS script, you should always state about it in the issue reports. And don't expect that your issue will be resolved.
 
 1. Add file `build/installer.nsh`.
-2. Define wanted macro to customise: `customHeader`, `preInit`, `customInit`, `customUnInit`, `customInstall`, `customUnInstall`, `customRemoveFiles`, `customInstallMode`, `customWelcomePage`.
+2. Define wanted macro to customise: `customHeader`, `preInit`, `customInit`, `customUnInit`, `customInstall`, `customUnInstall`, `customRemoveFiles`, `customInstallMode`, `customWelcomePage`, `customUnWelcomePage`.
 
     !!! example
         ```nsis
@@ -67,6 +67,12 @@ Keep in mind — if you customize NSIS script, you should always state about it
           # Welcome Page is not added by default for installer.
           !insertMacro MUI_PAGE_WELCOME
         !macroend
+
+        !macro customUnWelcomePage
+          !define MUI_WELCOMEPAGE_TITLE "custom title for uninstaller welcome page"
+          !define MUI_WELCOMEPAGE_TEXT "custom text for uninstaller welcome page $\r$\n more"
+          !insertmacro MUI_UNPAGE_WELCOME
+        !macroend
         ```
 
 * `BUILD_RESOURCES_DIR` and `PROJECT_DIR` are defined.

packages/app-builder-lib/templates/nsis/assistedInstaller.nsh

@@ -64,7 +64,12 @@
   !endif
 !else
   !ifndef removeDefaultUninstallWelcomePage
-    !insertmacro MUI_UNPAGE_WELCOME
+    !ifmacrodef customUnWelcomePage
+      !insertmacro customUnWelcomePage
+    !else
+      !insertmacro MUI_UNPAGE_WELCOME
+  !endif
+
   !endif
   !ifndef INSTALL_MODE_PER_ALL_USERS
     !insertmacro PAGE_INSTALL_MODE