Improve documentation clarity of texture methods

[JetStarBlues]

Minor changes to the wording used in the following texture methods, with the goal of improving clarity.

texture()

1) Reword

Current:

Texture for geometry. You can view other possible materials in this example.

Change:

Sets the texture that will be used to render subsequent shapes.

Note, texture() can only be used in WEBGL mode.

You can view more materials in this example.

2) Reword

Current:

2-dimensional graphics to render as texture

Change:

image to use as texture

3 @alt

Change:

spinning cube with a texture from an image

plane with a texture from an image created by createGraphics()

rectangle with video as texture

textureMode()

x) Omit disclaimer

Current:

This function only works in WEBGL mode.

2 @alt

Change:

quad with a texture

Screenshots of the change

texture

textureMode

textureWrap

[JetStarBlues]

Added some notes to texture() from the "Getting started with WebGL in p5" wiki. Added an extra example to demonstrate additional info.

updated texture()

Stumbled upon a "hidden" example for textureMode(). It is supposed to show use of IMAGE.