feat(lexer): implement numericEntity lexer

test/Spec.hs

@@ -30,6 +30,7 @@ main = hspec $ do
             it "bird tracks" birdTracks
             it "module names" modules
             it "quotes" quotes
+            it "numeric entity" numericEntity
             it "ignores nesting" ignoreNesting
 
     describe "Parser" do
@@ -152,6 +153,18 @@ space = do
                       , (1, 2, Newline)
                       ]
 
+numericEntity :: Expectation
+numericEntity = do
+    "A λ"
+        `shouldLexTo` [ (1, 1, NumericEntity 65)
+                      , (1, 6, Space)
+                      , (1, 7, NumericEntity 955) -- lambda
+                      ]
+    -- Hex
+    "e"
+        `shouldLexTo` [ (1, 1, NumericEntity 101)
+                      ]
+
 monospace :: Expectation
 monospace =
     "@mono@"