last task proposal issue template refinements

see SOI/experimental-projects#3 (comment)

.gitea/issue_template/proposal.yaml

@@ -2,24 +2,9 @@ name: Task Proposal
 about: Propose an idea for a task to be used in contests at SOI.
 labels:
   - task
+  - task/round/any
+  - task/difficulty/any
 body:
-  - type: markdown
-    attributes:
-      value: |
-        Thanks for taking the time to propose a task!
-        Do not forget to **update the issue title** with your unique task name.
-  - type: textarea
-    id: task
-    attributes:
-      label: Task description
-      description: "Formal problem statement.  Optional: Add your story idea."
-    validations:
-      required: true
-  - type: textarea
-    id: subtasks
-    attributes:
-      label: Subtasks
-      description: Possible subtasks or variations of the task.
   - type: input
     id: author
     attributes:
@@ -28,6 +13,27 @@ body:
       placeholder: stofl, inspired by https://codeforces.com/problemset/problem/1/A
     validations:
       required: true
+
+  - type: markdown
+    attributes:
+      value: |
+        Thanks for taking the time to propose a task!
+        Do not forget to **update the issue title** with your unique task name.
+  
+  - type: textarea
+    id: task
+    attributes:
+      label: Task description
+      description: "Formal problem statement.  Optional: Add your story idea."
+    validations:
+      required: true
+
+  - type: textarea
+    id: subtasks
+    attributes:
+      label: Subtasks
+      description: Possible subtasks or variations of the task.
+
   - type: input
     id: spoiler-begin
     attributes:
@@ -35,6 +41,7 @@ body:
       description: Opening the spoiler tag to hide solution and topic ideas, preventing accidential spoiling.
       placeholder: <details><summary>Topic Tags</summary>
       value: <details><summary>Topic Tags</summary>
+
   - type: dropdown
     id: round
     attributes:
@@ -131,18 +138,29 @@ body:
         - warmup
     validations:
       required: false
+
+  - type: input
+    id: topics-freeform
+    attributes:
+      label: "Topics (free-form)"
+      description: "Additional topics which are not available in the dropdown."
+    validations:
+      required: false
+
   - type: markdown
     attributes:
       value: |
         ### Rounds
         Which rounds would this task be applicable?
         Choose the corresponding *round* label(s) for this issue on the right.
+
   - type: markdown
     attributes:
       value: |
         ### Difficulty
         How would you rate the difficulty of this task?  Relative to the highest round you selected.
         Choose the corresponding *difficulty* label for this issue on the right.
+
   - type: textarea
     id: solution
     attributes:
@@ -150,6 +168,7 @@ body:
       description: Solution idea or possible approaches.  You don't need to have a full solution to propose a task, but please write down a few thoughts about how you would approach the task.
     validations:
       required: true
+
   - type: input
     id: spoiler-end
     attributes: