Documentation
* docs: add example for using laplacian, sobel and robert filter
- Also add images for the example ([`9566a11`](https://github.com/Preet-Sojitra/imgcv/commit/9566a11773d792fd2abe2aae30ab534128040be6))
Feature
* feat(filters): add more linear filters
- Add laplacian, sobel, and robert cross filters
- Add a utility function to apply padding and convolution ([`6958032`](https://github.com/Preet-Sojitra/imgcv/commit/69580326a52edc7bb925e9531078c8cd043b51e6))