feat(isMobilePhone): change the german prefix from '+490' to '+49' or '0'

[AnnaMariaJansen]

This would fix #1670

As described mobile phone numbers in Germany start with a 0 prefix such as 0157xxxxxxx. However the preceding 0 is dropped if the country code prefix +49 is added. Therefore I restrict the regex to +49 or 0 and no +490.

I adjusted the tests and added a '0' as validation to '15123456789'.

Examples
invalid:
'15123456789'
valid:
'+4915123456789'
'015123456789'

Checklist

• [ x] PR contains only changes related; no stray files, etc.
• [ x] README updated (where applicable)
• [ x] Tests written (where applicable)

[codecov]

Codecov Report

Merging #1679 (39df426) into master (907bb07) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master     #1679   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          101       101           
  Lines         1854      1854           
=========================================
  Hits          1854      1854           

Impacted Files	Coverage Δ
src/lib/isMobilePhone.js	100.00% <ø> (ø)

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[tux-tn]

LGTM! Thank you for your contribution @AnnaMariaJansen . The difference between your PR and #1675 is that numbers like 15623456789 are not valid anymore?

[Burnett01]

The problem with this PR is that it doesn't resolve the fundamentally wrong implementation of german mobile phone numbers. Local landline numbers (Berlin) are still valid. A more in-depth explanation can be found here:

#1670 (comment)

[AnnaMariaJansen]

LGTM! Thank you for your contribution @AnnaMariaJansen . The difference between your PR and #1675 is that numbers like 15623456789 are not valid anymore?

We use the validator for our application and that was our main issue. Yes. These numbers should not be valid in any case.

[profnandaa]

LGTM, thanks for the catch!