beginShape() documentation lack LINE_STRIP shape mode

Issue description

Examples shown encourage users who wants to draw multiple consecutive line segments to use "With no mode specified, the shape can be any irregular polygon".

But the default POLYGON mode doesn't work if user supply only 2 vertices...

The example code is working with four vertices, but doesn't work anymore if you comment two of them !

URL(s) of affected page(s)

https://processing.org/reference/beginShape_.html

Proposed fix

The fourth example should use beginShape(LINE_STRIP) and LINE_STRIP should be mentionned in mode's list.

noFill();
beginShape(LINE_STRIP);
vertex(30, 20);
vertex(85, 20);
endShape();

从受影响的 beginShape() 参考页面 https://processing.org/reference/beginShape_.html 开始，检查其中的第四个示例和形状模式列表。更新该示例以使用 LINE_STRIP，并在列表中提及该模式，然后验证渲染后的文档和包含两个顶点的示例。