When someone creates an invalid `queries` entry in the codeql config
file, like this:

```
queries:
  - foo.ql
```

THe error message is confusing, looking like this:

```
  Error: Cannot use 'in' operator to search for 'uses' in ql/ql/src
  TypeError: Cannot use 'in' operator to search for 'uses' in ql/ql/src
      at loadConfig (/home/runner/work/_actions/github/codeql-action/71a8b35ff4c80fcfcd05bc1cd932fe3c08f943ca/lib/config-utils.js:577:41)
```

With this change, the error message is more comprehensible:

`queries must be an array, with each entry having a 'uses' property`

Handle other cases where the config is invalid.

…rror-message

Co-authored-by: Henry Mercer <henrymercer@github.com>