chore: improve windows ux

[lincolnthalles]

gup requires you to type the full binary name under Windows, which is a little annoying.
At first, I thought it was an issue with GOPATH.

> gup update buf
gup:WARN : not found 'buf' package in $GOPATH/bin or $GOBIN
gup:ERROR: unable to update package: no package information or no package under $GOBIN

> gup update buf.exe
gup:INFO : update binary under $GOPATH/bin or $GOBIN
gup:INFO : [1/1] github.com/bufbuild/buf/cmd/buf (Already up-to-date: v1.27.0)

This PR:

• Improves bug-report command: launch in default browser instead of forcing msedge.
• Makes possible to use gup update buf, gup update buf.exe and even mix syntaxes:

.\gup.exe update buf.exe goreleaser
gup:INFO : update binary under $GOPATH/bin or $GOBIN
gup:INFO : [1/2] github.com/bufbuild/buf/cmd/buf (Already up-to-date: v1.27.0)
gup:INFO : [2/2] github.com/goreleaser/goreleaser (Already up-to-date: v1.21.2)

[nao1215]

@lincolnthalles

Thank you for the pull request.
I intend to merge the PR once the tests pass. good improvement.