chore: more accurate vim swap file ignore (#3707)

Newbrict · haoqunjiang · commit a575def3f21f · 2019-04-09T00:44:53.000+08:00
Currently this ignores more than the possible 3 character vim swap file extensions. This change will only ignore 3 letter vim swap files starting with `.sw` (most common)
diff --git a/packages/@vue/cli-service/generator/template/_gitignore b/packages/@vue/cli-service/generator/template/_gitignore
@@ -28,4 +28,4 @@ yarn-error.log*
 *.ntvs*
 *.njsproj
 *.sln
-*.sw*
+*.sw?

-Original file line number
+Diff line change
 *.ntvs*
 *.njsproj
 *.sln
 -*.sw*
 +*.sw?