Floating point exponent representation causing issues with imports

[glynternet]

Hi @tkrajina, Thanks so much for the package, it's super useful.

One issue I've been having is with output from the package containing floating point exponent representations like the following

<trkpt lat="51.581485" lon="5.6e-05">

which can be resolved by changing to the following:

<trkpt lat="51.581485" lon="0.000056">

This can be resolved with the change shown in https://github.com/glynternet/gpxgo/commit/314c84573cbc7ed0ab609b95008faea378709ac9.

I'm wondering whether you believe this is something that we could include in the codebase.

Garmin Basecamp is one of the applications that I've not been able to import files into when using gpxgo to serialise their content.