feat: Add GitHub Actions workflow for running tests on backend/core (#2822)

# Description

Please include a summary of the changes and the related issue. Please
also include relevant motivation and context.

## Checklist before requesting a review

Please delete options that are not relevant.

- [ ] My code follows the style guidelines of this project
- [ ] I have performed a self-review of my code
- [ ] I have commented hard-to-understand areas
- [ ] I have ideally added tests that prove my fix is effective or that
my feature works
- [ ] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged

## Screenshots (if appropriate):

.github/workflows/backend-core-tests.yml

@@ -7,6 +7,7 @@ on:
   pull_request:
     paths:
       - 'backend/core/**'
+  workflow_dispatch:
 
 jobs:
   test:
@@ -19,9 +20,9 @@ jobs:
           - 9998:9998
         options: >-
           --health-cmd="curl --fail http://localhost:9998/tika" 
-          --health-interval=10s 
-          --health-timeout=5s 
-          --health-retries=5
+          --health-interval=30s 
+          --health-timeout=10s 
+          --health-retries=10
 
     steps:
     - name: Checkout code

backend/core/README.md

@@ -1,5 +1,7 @@
 # quivr-core package
 
+The RAG of Quivr.com
+
 ```
 poetry install -E base
 ```