fix: directly specify location of package.json missing i18n config

[ChazUK]

I found it a bit hard trying to track down bad package.json files when using this across a large project with many scopes. This change clarifies which package.json has failed the check for i18n config.

PR Checklist

• The commit message follows our guidelines: https://github.com/ngneat/transloco/blob/master/CONTRIBUTING.md#commit

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[x] Other... Please describe:

What is the current behavior?

Console output when bad package.json is used only says package.json missing ...

What is the new behavior?

Output contains package.json location by using the lib.src parameter.

Does this PR introduce a breaking change?

[ ] Yes
[x] No