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();

Start with the affected beginShape() reference page at https://processing.org/reference/beginShape_.html and inspect its fourth example and shape-mode list. Update the example to use LINE_STRIP and mention that mode in the list, then verify the rendered documentation and the two-vertex example.