Word2007 Writer : Fixed first footnote appearing as separator

[jacksleight]

Description

Fixes #2634

This issue is caused by conflicting w:ids in the footnote data:

<w:footnote w:id="0" w:type="continuationSeparator">
  <w:p>
    <w:r>
      <w:continuationSeparator/>
    </w:r>
  </w:p>
</w:footnote>
<w:footnote w:id="0">
  ...
</w:footnote>

The continuation separator and the first footnote have the same w:id.

I tested how Word saves these and the footnotes start with a w:id of 1 not 0, so I just added that offset. I don't know if that's necessarily the best way to fix it (this is my first PHPWord PR), can make any changes if needed.

I also added new assertions to the footnotes test, to check that a footnote with w:id 0 does not exist and 1 does, but again, not sure if this is the best way to do that check.

Checklist:

• My CI is 🟢
• I have covered by unit tests my new code (check build/coverage for coverage report)
• I have updated the documentation to describe the changes
• I have updated the changelog

[coveralls]

coverage: 97.01%. remained the same
when pulling 965f688 on jacksleight:fix/footnote-seperator
into 1691301 on PHPOffice:master.

[Progi1984]

@jacksleight Hi, thank you for your contribution.

Could you update the 2.0.0.md changelog, please ?

[jacksleight]

@Progi1984 Ah yeah, that's done.

[Progi1984]

A last comment

[Progi1984]

Thank you @jacksleight for your contribution