Change current index when editing a test case.

src/routes/index.svelte

@@ -196,6 +196,7 @@
             mode: "test_case",
             testCaseIndex: parseInt(match[1]),
           }
+          $testCaseIndex = editionMode.testCaseIndex
           return
         }
       }
@@ -210,6 +211,7 @@
             testCaseIndex: parseInt(match[1]),
             variableName: match[2],
           }
+          $testCaseIndex = editionMode.testCaseIndex
           return
         }
       }