launch-editor: `fs.existsSync()` existence check can be bypassed on Windows

launch-editor allows users to open files with line numbers in editor from Node.js. Prior to 2.14.2, launch-editor-middleware processes an attacker-controlled Windows file argument where the file argument ends in a parent-directory component plus a line-and-column suffix: the path is resolved while the suffix is still present, and launch-editor removes the suffix before its existsSync check, leaving the existing parent directory for existsSync and allowing the attacker-controlled file argument to pass filename existence validation without requiring the malicious filename to exist. The bypass can lead to OS command injection when combined with the separately described Windows percent-expansion flaw. This issue is fixed in version 2.14.2.