Incorrect path to issue template file on windows

[crackedmind]

Description

after choosing template from the list issue body is empty, because template query parameter is wrong

?template=.gitea%5cISSUE_TEMPLATE%5cbug.md instead of ?template=.gitea%2fISSUE_TEMPLATE%2fbug.md

Manual fixing %5c to %2f in url helps

Gitea Version

1.18-rc1

Can you reproduce the bug on the Gitea demo site?

No

Log Gist

No response

Screenshots

No response

Git Version

No response

Operating System

Windows

How are you running Gitea?

From official gitea-1.18.0-rc1-windows-4.0-amd64.exe

Database

SQLite

[KazzmanK]

Looks similar to 21632

[zeripath]

Likely regression of #21639.

Paths in Git are always '/' separated.