Fix CSP script-src 'self'

[denhaandrei]

Fix CSP issue: https://github.com/swimlane/ngx-datatable/issues/1560

What kind of change does this PR introduce? (check one with "x")

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

What is the current behavior? (You can also link to an open issue here) https://github.com/swimlane/ngx-datatable/issues/1560

What is the new behavior?

Does this PR introduce a breaking change? (check one with "x")

• [ ] Yes
• [ x ] No

If this PR contains a breaking change, please describe the impact and migration path for existing applications: ...

Other information:

[GJBisschop]

Would it be possible to merge this PR? Thanks in advance!