Add icons to the system

[jecisc]

We often need to manage custom icons in Pharo.

Maybe we could have a page on icons management and explain how to add our own icons.

One way to do it is to do:

ThemeIcons compile:  'myLogoContents
	^ ''' , (Base64MimeConverter mimeEncode: 'logo.png' asFileReference binaryReadStream) contents , '''' classified: 'Material-Design-Lite-Core'.
	
ThemeIcons compile: 'myLogoIcon
	^ icons
			at: #''myLogoIcon''
			ifAbsentPut:[ Form fromBinaryStream: self myLogoContents base64Decoded asByteArray readStream ]' classified: 'Material-Design-Lite-Core'.

Smalltalk ui icons myLogoIcon

[juliendelplanque]

Favor usage of #binaryReadStreamDo: to ensure the resources are closed.