Prepopulate issue title from template file

Description

We cannot use the slash command /title in a template, because the title input is required to submit the new issue and the slash command is interpreted after the submission. Sometimes in templates, it could be usefull to generate a title or a part of it.

Proposal

2 propositions :

• when selecting a template, it can be parsed to search for a /title and apply it
• the form validation need to parse the description and search for a /title (not empty) and allow the form submission

Links / references

Documentation blurb

1. Why should someone use it; what's the underlying problem.
   Making possible the use of the /title inside a template could improve the template interest. Especially for reccurrent issues...
2. What is the solution.
   In a template, when using a /title it will be used as the title of the created issue
3. How does someone use this
   /title Make possible the use of /title inside a template