feat: Update process documentation, issue templates (nginx#1409)

This commit adds NGINX Unit to the deprecated content process document,
and updates the issue templates to reduce the amount of mandatory fields
and rephrase questions to be more open-ended in the bug report and idea
forms, accounting for simpler issues.

It also removes some leftover include files related to products whose
main content folders have already been removed.

Author: ADubhlaoich

.github/ISSUE_TEMPLATE/1-idea_suggestion.yml

@@ -10,7 +10,7 @@ body:
       required: true
   - type: dropdown
     attributes: 
-      label: Which product or products does this request relate to?
+      label: Which product or products does this idea relate to?
       multiple: true
       options:
         - F5 DoS for NGINX
@@ -28,16 +28,12 @@ body:
       required: true
   - type: textarea
     attributes:
-      label: Is this idea related to a larger problem?
+      label: Does this idea relate to other issues?
       description: If you have identified multiple related issues, it might be a design pattern problem.
-    validations:
-      required: true
   - type: textarea
     attributes: 
-      label: What alternative ways are there to implement your idea?
-      description: There are often multiple ways to something - context is important.
-    validations:
-      required: true
+      label: Are there alternative ideas for improving the same topic?
+      description: If you already identified reasons not to go with other solutions, we'd like to know why!
   - type: textarea
     attributes: 
       label: Any additional information

.github/ISSUE_TEMPLATE/2-bug_report.yml

@@ -1,16 +1,16 @@
 name: Bug report
-description: Report an issue with our documentation
+description: Report an issue with our content or website
 title: "[Bug]: "
 body: 
   - type: textarea
     attributes:
-      label: Describe the bug you have identified
+      label: Describe the problem you have identified
       description: Explain the problem with as much detail as possible.
     validations:
       required: true
   - type: dropdown
     attributes: 
-      label: Which product or products does this request relate to?
+      label: Which product or products does this problem relate to?
       multiple: true
       options:
         - F5 DoS for NGINX
@@ -28,22 +28,16 @@ body:
       required: true
   - type: textarea
     attributes:
-      label: Steps to reproduce the bug
+      label: If necessary, explain any additional steps to reproduce the problem.
       description: Describe the where the issue occurs.
-    validations:
-      required: true
   - type: textarea
     attributes:
       label: What is the expected or desired behaviour?
-      description: Describe what you expected to happen instead of the bug.
-    validations:
-      required: true    
+      description: Describe what you expected to happen instead of the problem
   - type: textarea
     attributes:
-      label: What environments or versions does this bug affect?
-      description: Describe the contexts which this bug seems to occur.
-    validations:
-      required: true
+      label: Is this problem specific to a particular platform or software version?
+      description: Describe the context in which this problem appears.
   - type: textarea
     attributes: 
       label: Any additional information