fix: add a missing check for inject-field diagnostics

Author: NeOzay

script/core/diagnostics/inject-field.lua

@@ -68,6 +68,9 @@ return function (uri, callback)
             if def.type == 'doc.field' then
                 return
             end
+            if def.type == 'tablefield' then
+                return
+            end
         end
 
         local howToFix = ''

test/diagnostics/inject-field.lua

@@ -82,3 +82,16 @@ function m:init() -- OK
     end
 end
 ]]
+
+TEST [[
+---@class Class
+local m = {
+    xx = 1, -- OK
+}
+
+---@type Class
+local m
+
+m.xx = 1 -- OK
+m.<!yy!> = 1 -- Warning
+]]