[Minor] Add additional bad attachment types

- app: Executable Application, blocked in Outlook by default
- aspx: Active Server Page Extended, blocked in Outlook by default
- dll: Dynamic-link Library
- dqy: Microsoft Query File, blocking recommended in MS365
- iqy: ditto
- mht: MHTML File, often abused for phishing and exploit attempts
- mhtml: ditto
- oqy: Microsoft Query File, blocking recommended in MS365
- rqy: ditto
- slk: Microsoft Symbolic Link
- wim: Windows Imaging Format

src/plugins/lua/mime_types.lua

@@ -63,12 +63,23 @@ local settings = {
     shtml = 1,
     -- Have you ever seen that in legit email?
     ace = 4,
+    app = 1,
     arj = 2,
+    aspx = 1,
     asx = 2,
     cab = 3,
+    dll = 4,
+    dqy = 2,
+    iqy = 2,
+    mht = 2,
+    mhtml = 2,
+    oqy = 2,
+    rqy = 2,
     sfx = 2,
+    slk = 2,
     vst = 2,
     vss = 2,
+    wim = 2,
     -- Additional bad extensions from Gmail
     ade = 4,
     adp = 4,