Fix link in PR template [skip ci]

Author: FabijanC

.github/pull_request_template.md

@@ -10,7 +10,7 @@
 
 <!-- If you are not able to complete one of these steps, you can still create a PR, but note what caused you trouble. -->
 
-- [ ] Checked out the [contribution guidelines](CONTRIBUTING.md)
+- [ ] Checked out the [contribution guidelines](https://github.com/0xSpaceShard/starknet-devnet/blob/main/.github/CONTRIBUTING.md)
 - [ ] Applied formatting - `./scripts/format.sh`
 - [ ] No linter errors - `./scripts/clippy_check.sh`
 - [ ] No unused dependencies - `./scripts/check_unused_deps.sh`