add short titles to frontmatter (#20131)

content/github/importing-your-projects-to-github/working-with-subversion-on-github/index.md

@@ -10,5 +10,6 @@ children:
   - /what-are-the-differences-between-subversion-and-git
   - /support-for-subversion-clients
   - /subversion-properties-supported-by-github
+shortTitle: Work with Subversion on GitHub
 ---
 

content/github/importing-your-projects-to-github/working-with-subversion-on-github/subversion-properties-supported-by-github.md

@@ -7,6 +7,7 @@ redirect_from:
 versions:
   fpt: '*'
   ghes: '*'
+shortTitle: Properties supported by GitHub
 ---
 ## Executable files (svn:executable)
 

content/github/importing-your-projects-to-github/working-with-subversion-on-github/support-for-subversion-clients.md

@@ -7,6 +7,7 @@ redirect_from:
 versions:
   fpt: '*'
   ghes: '*'
+shortTitle: Support for Subversion clients
 ---
 GitHub supports Subversion clients via the HTTPS protocol. We use a Subversion bridge to communicate svn commands to GitHub.
 

content/github/importing-your-projects-to-github/working-with-subversion-on-github/what-are-the-differences-between-subversion-and-git.md

@@ -8,6 +8,7 @@ redirect_from:
 versions:
   fpt: '*'
   ghes: '*'
+shortTitle: Subversion & Git differences
 ---
 ## Directory structure