upgrade petitparser to 5.0.0

[alexmarkley]

Allows upgrades to petitparser 5.0.0, which enables version solving with newer versions of xml.

Solves problems like:

Because expressions >=0.2.0 depends on petitparser ^4.0.2 and xml >=5.4.0 depends on petitparser ^5.0.0, expressions >=0.2.0 is incompatible with xml >=5.4.0.
And because flutter_svg >=1.1.0 depends on xml ^6.0.1, expressions >=0.2.0 is incompatible with flutter_svg >=1.1.0.
So, because someapp depends on both flutter_svg ^1.1.0 and expressions ^0.2.3, version solving failed.

[alexmarkley]

I think this PR solves https://github.com/appsup-dart/expressions/issues/22

[droplet-js]

any news update ... i have same issue ...

[rbellens]

fixed in v0.2.4 already