Vim undefined variable
# Description

Usage of themer along with @themer/vim causes undefined variable errors

# To reproduce

Steps to reproduce the behavior:

1. Use themer template
2. generate

## Screenshots

![image](https://user-images.githubusercontent.com/55749227/95399095-61650a00-08d5-11eb-9176-6e2ad9303401.png)

## Expected behavior

No errors

# Environment information

## CLI

Please fill out the following information if you are using the command-line interface. For the web UI, you can delete this section.

* Device [e.g. iPhone6, MacBook Pro]: MacBook Air
* OS [e.g. iOS, macOS]: Arch Linux
* OS version [e.g. 14.0]: Linux 5.8.13, Latest Arch
* Node version [e.g. 14.4.0]: 14.13.0
* `themer` version [e.g. 3.3.4]: 3.3.4
* Other `themer` packages and their versions [e.g. `@themer/vscode@2.2.1`]: @themer/vim@3.3.0
* Vim version: 8.2

# Additional context

Here's my config file
```js
module.exports.colors = {
    dark: {
        accent0: "#FF4050",
        accent1: "#F28144",
        accent2: "#FFD24A",
        accent3: "#A4CC35",
        accent4: "#26C99E",
        accent5: "#66BFFF",
        accent6: "#CC78FA",
        accent7: "#F553BF",
    
        shade0: "#282629",
        shade1: "#474247",
        shade2: "#656066",
        shade3: "#847E85",
        shade4: "#A29DA3",
        shade5: "#C1BCC2",
        shade6: "#E0DCE0",
        shade7: "#FFFCFF",
    },
}
```

The problem is the if statement causing the variable to be scoped locally
```vim


  
  if &background == 'dark'
    
  let s:guishade0 = "#282629"
  let s:guishade1 = "#474247"
  let s:guishade2 = "#656066"

  . . .
  
  endif
```

I know the `s:` is supposed to scope the variable to the script, but for some reason, I get those errors. If I remove the if statements, themer works.