fix: add AppliedTradeTax to LogisticsServiceCharge (backport #34)

[mergify]

Adding shipping costs as taxes with charge type "Actual" and VAT on the next line with charge type "On Previous Row Amount" or "On Previous Row Total" will produce an invalid e-invoice xml file with the extended profile.

The validation on import in erpnext will fail with the error

[BR-FXEXT-S-08]-For each different value of VAT category rate (BT-119) where the VAT category code (BT-118) is equal to “S” ("Standard rated"), Absolute Value of (VAT category taxable amount (BT-116) - ∑ Invoice line net amounts (BT-131) + Σ Document level allowance amounts (BT-92) - Σ Document level charges amounts (BT-99) - Σ Logistics Service fee amounts (BT-x-272)) <= 0,01 * ((Number of line net amounts (BT-131) + Number of Document level allowance amounts (BT-92) + Number of Document level charge amounts (BT-99) + Number of Logistics Service fee amounts (BT-X-272)), where the VAT category code (BT-151, BT-95, BT-102, BT-X-273) is "Standard rated" (S) and the VAT rate (BT-152, BT-96, BT-103, BT-X-274) equals the VAT category rate (BT-119).
Element 'ram:AppliedTradeTax' must occur at least 1 times.

In order to fix this, output SpecifiedLogisticsServiceCharge with AppliedTradeTax.

      <ram:SpecifiedLogisticsServiceCharge>
        <ram:Description>DHL Paket bis 5 kg</ram:Description>
        <ram:AppliedAmount>5.99</ram:AppliedAmount>
        <ram:AppliedTradeTax>
          <ram:TypeCode>VAT</ram:TypeCode>
          <ram:CategoryCode>S</ram:CategoryCode>
          <ram:RateApplicablePercent>19.0</ram:RateApplicablePercent>
        </ram:AppliedTradeTax>
      </ram:SpecifiedLogisticsServiceCharge>
```<hr>This is an automatic backport of pull request #34 done by [Mergify](https://mergify.com).