ci(core): fix path filtering on ci_skipped workflow. (#1354)

**Motivation**
We want `ci_skipped` to run whenever there were changes to doc files,
but we don't want to run it if there are changes to code.

See documentation:
https://docs.github.com/en/actions/writing-workflows/workflow-syntax-for-github-actions#example-including-and-excluding-paths

.github/workflows/ci_skipped.yaml

@@ -7,6 +7,14 @@ on:
       - 'LICENSE'
       - "**/README.md"
       - "**/docs/**"
+      - '!**/*.rs'
+      - '!**/*.toml'
+      - '!**/*.yaml'
+      - '!**/*.sh'
+      - '!**/*.json'
+      - '!**/*.rlp'
+      - '!**Dockefile'
+      - '!**Makefile'
 jobs:
   lint:
     # "Lint" is a required check, don't change the name