Feature Request: Expose Flags/Vars to Templating

It would be quite neat if we could call the other global vars defined in the main.go when writing our Go templates.
Perhaps in turn call our comment data type explicitly. (i.e. `{{.comment}}`
`token,owner,repo,commentType,sha,number,file,position,templ,format,comment,deleteCommentRegex,baseURL,uploadURL`

Example Template:

```
## Things Deployed to Platform in #{{.number}}
This is a test of the emergency broadcast system, this is only a test.

#A Header about the things we are deploying
{{.comment}} - `A body that is generated in via bash`
```

If I am reading `func formatComment(comment string) (string, error)` correct, presently it passes `comment` to the formatter explicitly.

Start in main.go and trace func formatComment(comment string) (string, error) to see how the Go template is currently given comment data. Check how the listed globals are defined and passed into formatting. Done means templates can access the requested vars, including comment data, and the example template renders as intended.

索引モデルが issue の本文から書いたものです。