Fix/german mobile phone validation

[Burnett01]

fix(isMobilePhone) german: Restrict leading zero when country code +49 is used

This PR ensures that german mobile phone numbers are deemed invalid when the country code (+49) is used with a leading 0.

Example:

Invalid: +4901575663214
Valid: +491575663214

See #1670

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 #1675 (3e0742f) into master (907bb07) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master     #1675   +/-   ##
=========================================
  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)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 907bb07...3e0742f. Read the comment docs.

[profnandaa]

Sorry this was already addressed in #1679 and sorry for late review // but thanks for your contribution!