Update and create new issue templates for better ctageorisation

[128 of 600 issues are just questions and support and this is getting out of hand IMHO](https://github.com/PrivateBin/PrivateBin/issues?q=is%3Aissue+is%3Aopen+label%3Aquestion%2Fsupport), so I thought we need to do something while of course IMHO keeping support in some sense that is vital to an open-source project.

Anyway, this here now:
* Converts the "one and only issue template" to multiple ones with the new GitHub way, see https://docs.github.com/en/communities/using-templates-to-encourage-useful-issues-and-pull-requests/
  Note this uses mostly the templates they have, modifies them to use proper headers (sorry but I don't get why they always want to use **bold text** as headers, when you have real markdown headings) and adjusts/ports the
* We could use even more elaborate issue forms, but that  was too much for me to do now and is also beta, so maybe when they have a visual editor for that or so 😉 https://docs.github.com/en/communities/using-templates-to-encourage-useful-issues-and-pull-requests/configuring-issue-templates-for-your-repository#creating-issue-forms

The aim:
* is to get support requests and stuff directly sorted and tagged, so they are out the way
* is to nudge people to improve the quality of issues/reports by providing a more useful template or their use case
* is to redirect people to the appropriate resource (give me a moment)

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,22 @@
+---
+name: Feature request
+about: Suggest an idea for this project
+title: ''
+labels: enhancement
+assignees: ''
+
+---
+
+## The problem
+
+<-- Is your feature request related to a problem? Please describe.
+A clear and concise description of what the problem is. Ex. I'm always frustrated when -->
+
+## The solution
+<-- A clear and concise description of what you want to happen. Pitch your solution! What would happen, if we don't implement this? -->
+
+## Alternatives
+<!-- A clear and concise description of any alternative solutions or features you've considered. -->
+
+## Additional context
+<!-- Add any other context or screenshots about the feature request here. -->