fix Qt version 5.15.2

CONTRIBUTING.md

@@ -1,6 +1,6 @@
 # Contributing code
 
-Thanks for contributing to Seamly code, documentation, translations, website, and wiki! 
+Thanks for contributing to Seamly code, documentation, translations, website, and wiki!
 
 Our workflow is based on **Git Flow**, outlined in the steps below.    
 As always, please fix only one issue at a time.   
@@ -9,12 +9,12 @@ Build your branch with Qt and test, then make a pull request.
 Read more about **Git Flow**:  http://nvie.com/posts/a-successful-git-branching-model/   
 Read more about **Pull Requests**: https://help.github.com/articles/about-pull-requests/ and https://help.github.com/articles/creating-a-pull-request/    
 
-## Naming conventions 
+## Naming conventions
 
 Name your branch after the issue you will fix. Example: Name your branch **issue-#155** for issue #155.
 
-The permanent named branches on this repo are: 
-* **develop** - Contains next major release. Used for testing and sharing among developers. 
+The permanent named branches on this repo are:
+* **develop** - Contains next major release. Used for testing and sharing among developers.
 * **master** - Used only for releases.
 * **release-x.x.x** - Created from **develop**. Contains feature freeze state before the next major release. Used for preparing each major & minor release with updated build information. Merge to **master** with new tag to create a new release.
 * **hotfix-x.x.x** - Create from **develop** and **master**. Contains a quick emergency fix for big bugs. Merge to **master** (or **release**) and **develop**.
@@ -23,7 +23,7 @@ The permanent named branches on this repo are:
 
 * Clone the repo & set the origin URL
 >git clone https://github.com/fashionfreedom/seamly2d  
-git remote set-url origin https://github.com/fashionfreedom/seamly2d 
+git remote set-url origin https://github.com/fashionfreedom/seamly2d
 
 * Create your issue branch then switch focus to your issue branch. Examples use branch for issue #155.
 >git checkout develop       
@@ -32,27 +32,27 @@ git checkout issue-#155
 
 ## Daily workflow  
 
-* Pull latest changes from the origin **develop** branch & merge them into your issue branch 
+* Pull latest changes from the origin **develop** branch & merge them into your issue branch
 >git pull origin develop  
 git checkout issue-#155  
 git merge develop  
 
 * Make your code changes & commit your changes.  
 >git commit -a  
 git commit -m "fix bug with arc and line tool issue-#155"  
-git commit push issue-#155 
+git commit push issue-#155
 
 ## Create a Pull Request
 
-* Build & test your issue branch with Qt 5.13.2 & Qt Creator 4.3.x with compilers MSVC 2017, MinGW 7.3.0, gcc, or clang. 
+* Build & test your issue branch with Qt 5.15.2 & Qt Creator 4.3.x with compilers MSVC 2017, MinGW 7.3.0, gcc, or clang.
 
 * Push your issue branch up to the github repo.
->git push -u origin issue-#155 
+>git push -u origin issue-#155
 
-* Select **Branch:develop** then **Pull Requests** on the repo main menu bar. 
+* Select **Branch:develop** then **Pull Requests** on the repo main menu bar.
 * Select the green **New Pull Request** button then select your issue branch from the **Compare:develop** dropdown list.  
 * Enter the Pull Request Header as "tag: description issue_" using _conventional-changelog/commit-zen-cli_ tags so your commits are auto-included in the Changelog.md file. Read more here: https://docs.changelogg.io/conventional-changelog-template. Example PR Header: "fix: bug with Arc and line tool #issue-#155".    
- + Valid Tags are: 
+ + Valid Tags are:
     - fix
     - feat
     - build
@@ -63,7 +63,7 @@ git commit push issue-#155
     - refactor
     - revert
     - style
-    - test 
+    - test
 * Click the **Create Pull Request** button.
 * Select **Linked Issues** in the right hand column and select the issue. Example: select issue #155.  
 * The maintainer will check that all CI/CD tests passed, review the code, then merge your issue branch into **develop**.

src/app/seamlyme/main.cpp

@@ -64,7 +64,7 @@ int main(int argc, char *argv[])
     Q_INIT_RESOURCE(schema);
     Q_INIT_RESOURCE(flags);
 
-    QT_REQUIRE_VERSION(argc, argv, "5.13.2")
+    QT_REQUIRE_VERSION(argc, argv, "5.15.2")
 
     //------------------------------------------------------------------------
     // On macOS, correct WebView / QtQuick compositing and stacking requires running