Clarify README monomer description - #3

No file matched to [/home/runner/work/monomer-database-source/monomer-database-source/**/*requirements*.txt,/home/runner/work/monomer-database-source/monomer-database-source/**/*requirements*.in,/home/runner/work/monomer-database-source/monomer-database-source/**/*constraints*.txt,/home/runner/work/monomer-database-source/monomer-database-source/**/*constraints*.in,/home/runner/work/monomer-database-source/monomer-database-source/**/pyproject.toml,/home/runner/work/monomer-database-source/monomer-database-source/**/uv.lock,/home/runner/work/monomer-database-source/monomer-database-source/**/*.py.lock]. The cache will never get invalidated. Make sure you have checked out the target repository and configured the cache-dependency-glob input correctly.