Pin for Shader Editor

[SirPigeonz]

Godot 3.0 master

Pinning for Shader Editor is needed badly. :D
For now testing shader is really unpleasant. xD
If you do anything in 3D view, Shader Editor closes.
If you want to try your fresh new uniforms in material, switching to material in Inspector also closes Shader Editor.
This is madness :D

[nunodonato]

also #8069 ;)

[eon-s]

I wanted to edit the shader resource outside of Godot (could be another option) but the code is not updated by the editor 🙃

[reduz]

kicking to 3.1, no time to think out this properly

[Calinou]

Duplicate of #32002 (same cause).