Add demos to readmes (#16)

Author: Copilot

packages/eslint-formatter-checkstyle/expected-out

@@ -2,8 +2,8 @@
 
 > ESLint's `checkstyle` formatter as a standalone package
 
-## Links
+## Demo
 
-- [Formatter output example](examples)
-- [Source code](https://github.com/fregante/eslint-formatters/tree/main/packages/eslint-formatter-checkstyle)
-- [npm package contents](https://www.unpkg.com/browse/eslint-formatter-checkstyle/)
+```xml
+<?xml version="1.0" encoding="utf-8"?><checkstyle version="4.3"><file name="foo.js"><error line="5" column="10" severity="error" message="Unexpected foo. (foo)" source="eslint.rules.foo" /></file><file name="bar.js"><error line="6" column="11" severity="warning" message="Unexpected bar. (bar)" source="eslint.rules.bar" /></file><file name="baz.js"><error line="1" column="1" severity="error" message="Fatal error parsing file." source="" /></file></checkstyle>
+```

packages/eslint-formatter-checkstyle/readme.md

@@ -2,8 +2,12 @@
 
 > ESLint's `compact` formatter as a standalone package
 
-## Links
+## Demo
 
-- [Formatter output example](examples)
-- [Source code](https://github.com/fregante/eslint-formatters/tree/main/packages/eslint-formatter-compact)
-- [npm package contents](https://www.unpkg.com/browse/eslint-formatter-compact/)
+```
+foo.js: line 5, col 10, Error - Unexpected foo. (foo)
+bar.js: line 6, col 11, Warning - Unexpected bar. (bar)
+baz.js: line 1, col 1, Error - Fatal error parsing file.
+
+3 problems
+```

packages/eslint-formatter-compact/expected-out

@@ -2,8 +2,8 @@
 
 > ESLint's `jslint-xml` formatter as a standalone package
 
-## Links
+## Demo
 
-- [Formatter output example](examples)
-- [Source code](https://github.com/fregante/eslint-formatters/tree/main/packages/eslint-formatter-jslint-xml)
-- [npm package contents](https://www.unpkg.com/browse/eslint-formatter-jslint-xml/)
+```xml
+<?xml version="1.0" encoding="utf-8"?><jslint><file name="foo.js"><issue line="5" char="10" evidence="" reason="Unexpected foo. (foo)" /></file><file name="bar.js"><issue line="6" char="11" evidence="" reason="Unexpected bar. (bar)" /></file><file name="baz.js"><issue line="1" char="1" evidence="" reason="Fatal error parsing file." /></file></jslint>
+```

packages/eslint-formatter-compact/readme.md

@@ -2,8 +2,35 @@
 
 > ESLint's `json-with-metadata` formatter as a standalone package
 
-## Links
+## Demo
 
-- [Formatter output example](examples)
-- [Source code](https://github.com/fregante/eslint-formatters/tree/main/packages/eslint-formatter-json-with-metadata)
-- [npm package contents](https://www.unpkg.com/browse/eslint-formatter-json-with-metadata/)
+```json
+{
+	"results": [
+		{
+			"filePath": "foo.js",
+			"messages": [{"message": "Unexpected foo.", "severity": 2, "line": 5, "column": 10, "ruleId": "foo"}],
+			"errorCount": 1,
+			"warningCount": 0,
+			"fixableErrorCount": 0,
+			"fixableWarningCount": 0
+		},
+		{
+			"filePath": "bar.js",
+			"messages": [{"message": "Unexpected bar.", "severity": 1, "line": 6, "column": 11, "ruleId": "bar"}],
+			"errorCount": 0,
+			"warningCount": 1,
+			"fixableErrorCount": 0,
+			"fixableWarningCount": 0
+		},
+		{
+			"filePath": "baz.js",
+			"messages": [{"message": "Fatal error parsing file.", "severity": 2, "fatal": true, "line": 1, "column": 1, "ruleId": null}],
+			"errorCount": 1,
+			"warningCount": 0,
+			"fixableErrorCount": 0,
+			"fixableWarningCount": 0
+		}
+	]
+}
+```

packages/eslint-formatter-jslint-xml/expected-out

@@ -2,8 +2,33 @@
 
 > ESLint's `json` formatter as a standalone package
 
-## Links
+## Demo
 
-- [Formatter output example](examples)
-- [Source code](https://github.com/fregante/eslint-formatters/tree/main/packages/eslint-formatter-json)
-- [npm package contents](https://www.unpkg.com/browse/eslint-formatter-json/)
+```json
+[
+	{
+		"filePath": "foo.js",
+		"messages": [{"message": "Unexpected foo.", "severity": 2, "line": 5, "column": 10, "ruleId": "foo"}],
+		"errorCount": 1,
+		"warningCount": 0,
+		"fixableErrorCount": 0,
+		"fixableWarningCount": 0
+	},
+	{
+		"filePath": "bar.js",
+		"messages": [{"message": "Unexpected bar.", "severity": 1, "line": 6, "column": 11, "ruleId": "bar"}],
+		"errorCount": 0,
+		"warningCount": 1,
+		"fixableErrorCount": 0,
+		"fixableWarningCount": 0
+	},
+	{
+		"filePath": "baz.js",
+		"messages": [{"message": "Fatal error parsing file.", "severity": 2, "fatal": true, "line": 1, "column": 1, "ruleId": null}],
+		"errorCount": 1,
+		"warningCount": 0,
+		"fixableErrorCount": 0,
+		"fixableWarningCount": 0
+	}
+]
+```