Add narrow emptyset symbol (#132)

Author: mkorje

CHANGELOG.md

@@ -9,6 +9,8 @@
 ### New in `sym`
 
 - Mathematical symbols
+  - `emptyset.zero`: ∅︀
+  - `nothing.zero`: ∅︀
   - `union.serif`: ∪︀
   - `union.sq.serif`: ⊔︀
   - `inter.serif`: ∩︀

src/modules/sym.txt

@@ -417,12 +417,14 @@ asymp ≍
 
 // Set theory.
 emptyset ∅
+  .zero ∅\vs{1}
   .arrow.r ⦳
   .arrow.l ⦴
   .bar ⦱
   .circle ⦲
   .rev ⦰
 nothing ∅
+  .zero ∅\vs{1}
   .arrow.r ⦳
   .arrow.l ⦴
   .bar ⦱