Add unscoped variables fixer

selene-lib/src/lints/unscoped_variables.rs

@@ -60,8 +60,8 @@ impl Lint for UnscopedVariablesLint {
                         reference.name
                     ),
                     Label::new(reference.identifier),
-                    None,
-                    Applicability::Unspecified,
+                    Some(format!("local {}", reference.name)),
+                    Applicability::MaybeIncorrect,
                 ));
             }
         }

selene-lib/tests/lints/unscoped_variables/unscoped_variables.fixed.diff

@@ -0,0 +1,16 @@
+-[MI] bar = true
++[MI] local bar = true
+
+      local foo = 1
+      foo = 2
+
+      local bar = 1
+      bar = 2
+
+      pcall(function()
+          foo = 3
+-[MI]     baz = 1
++[MI]     local baz = 1
+      end)
+
+      _ = 3

selene-lib/tests/lints/unscoped_variables/unscoped_variables.stderr

@@ -3,10 +3,14 @@ error[unscoped_variables]: `bar` is not declared locally, and will be available
   │
 1 │ bar = true
   │ ^^^
+  │
+  = try: `local bar`
 
 error[unscoped_variables]: `baz` is not declared locally, and will be available in every scope
    ┌─ unscoped_variables.lua:11:5
    │
 11 │     baz = 1
    │     ^^^
+   │
+   = try: `local baz`