More generic post-processing route

Right now, as stated in docs https://github.com/armory3d/armory/wiki/renderpath#adding-post-processing-pass we need to edit files in SDK, what can lead to conflicts and lost data when updating the SDK. The feature request is to add a predefined directory in **project scope**, that also is iterated and its shaders are added to "shader_datas.arm" to be loaded later in custom render path without touching the SDK (maybe Bundled/Shaders/* ?)

Start with the post-processing documentation at the linked renderpath page and trace how SDK files and shader_datas.arm are currently handled. Evaluate the proposed project-scope directory, such as Bundled/Shaders/*, and define how its shaders would be iterated and included for custom render paths without modifying the SDK. Done means the project-level route is implemented and SDK updates no longer overwrite those shaders.

Written by the indexing model from the issue text.