Close Pen Tool path with double click

This option is handled differently in many applications. In most open source ones double clicking while making a path with Pen Tool equivalents either does not do anything (Gimp), or ends the path drawing without closing the path (Krita, Inkscape). In "industry standard" applications however it makes a new anchor under the cursor placement and closes the path. I think the latter is a good feature to have - especially for quick editing as it does not force user to precisely point at the path start to close it.

未指定文件或测试。首先定位 Pen Tool 路径交互的入口点及其现有的路径闭合行为；完成标准是双击会在光标下创建一个锚点并闭合路径，而不需要光标到达起点。

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