Add branch and tag filter

[changelog:added]

SETTINGS.md

@@ -72,6 +72,14 @@ Connect and configure these integrations:
     [semantic version][semver], the `latest` tag is added, making the published
     version the new default.
 
+1.  **Specify optional branch or tag filters**
+
+    Specify one or more regular expressions to match against the branch or tag
+    name of the skill trigger.
+
+    To limit this skill to only run on _feature_ branches, you could use the
+    `feature\/.*` regular expression as filter.
+
 1.  **Specify an optional bash command**
 
     ![Shell command](docs/images/shell-command.png)
@@ -81,7 +89,7 @@ Connect and configure these integrations:
     20.04 LTS container. This command is after the code is checked out but
     before Node.js is setup or any npm commands are run.
 
-    Here's is an example on how to install MongoDB and start it:
+    Here is an example on how to install MongoDB and start it:
 
     ```bash
     apt-get update \

skill.ts

@@ -26,7 +26,7 @@ import {
 import { Configuration } from "./lib/configuration";
 
 export const Skill = skill<
-	Configuration & { repos: any; subscription_filter: any }
+	Configuration & { repos: any; subscription_filter: any; ref_filter: any }
 >({
 	description: "Run npm scripts to compile or test your JavaScript project",
 	displayName: "npm Build",
@@ -118,6 +118,10 @@ export const Skill = skill<
 				"Register the published package with the given tags. If no tag is set here, the package will get published with a branch specific tag, e.g. `branch-<name of branch>`.",
 			required: false,
 		},
+		ref_filter: {
+			...parameter.refFilter(),
+			visibility: ParameterVisibility.Advanced,
+		},
 		command: {
 			type: ParameterType.String,
 			displayName: "Shell command",