Merge pull request micro-editor#3663 from niten94/sh-separate-paramexp

`sh.yaml`: Match valid parameter expansions without braces

Author: JoeKar

runtime/syntax/sh.yaml

@@ -41,8 +41,8 @@ rules:
       # Conditional flags
     - statement: "\\s+(-[A-Za-z]+|--[a-z]+)"
 
-    - identifier: "\\$\\{[0-9A-Za-z_:!%&=+#~@*^$?, .\\-\\/\\[\\]]+\\}"
-    - identifier: "\\$[0-9A-Za-z_:!%&=+#~@*^$?,\\-\\[\\]]+"
+    - identifier: "\\$\\{[\\w:!%&=+#~@*^$?, .\\-\\/\\[\\]]+\\}"
+    - identifier: "\\$([0-9_!#@*$?-]|[A-Za-z_]\\w*)"
 
     - constant.string:
         start: "\""