Tools: Add 'This week' and 'Next week' fields to weekly report generator

Fields that briefly show what you did this week and intend to do next
week are required, so it seems convenient to add a field and suggested
default information that can be edited by the user.

**Example of what is generated:**
```
**This week:** triaging, bug fixing and worked on:
* blender/blender!116799: Fix #105460: Overlay "Backwire Opacity" is 0.0 in new 3D Views
* blender/blender!116692: Fix #112599: Blender freezes for half a minute when opening File Browser

**Next Week:** Triaging, bug fixing and finalize pull requests.
```

@@ -187,0 +198,4 @@
+    # * blender/blender!{pull_number}: Title
+    did_triage = len(issues_confirmed) or len(issues_archived) or len(issues_duplicated)
+    did_fix = len(issues_fixed)
+    workded_on_pulls = len(pulls_worked)