Add new increment filter to Numbers

[FelipeDocil]

I'm using Sourcery, I can't create my own filters and I've tried many times to increment an Integer, I'd like to ask if it's possible to add this as a new filter for numbers here at StencilSwiftKit (or please help me how I'd achieve this without a new filter)

For context what I'd like to do in Stencil:
{{ forloop.counter + 5 }}

Unfortunately this is not yet supported (see for reference: stencilproject/Stencil#117)

I'd like to propose a new filter that would look similar to this:
{{ forloop.counter|increment:5 }}

Any thoughts? Again if I can do that with the existing filter please let me know