macOS Big Sur support

update macOS build instructions, travis no longer exists

Don't use const on image2d_t

Run GitHub workflow build on pull requests

User guide from HePTaset

added missing QPainterPath includes

Pushing a branch and creating a pull request would run all the builds twice with the previous formulation.

Trying the yml from here: https://github.community/t/how-to-trigger-an-action-on-push-or-pull-request-but-not-both/16662/3

fix typo on preset include

First Batch of Presets (ZCam S1, GoPro Fusion, Yi360)