Fix fleet package generation (#1296)

* Fix fleet package generation
* Add .lstrip()
* Lint fix
* Add newline

detection_rules/packaging.py

@@ -471,9 +471,9 @@ class Package(object):
         manifest_file = package_dir / 'manifest.yml'
         readme_file = docs_dir / 'README.md'
         notice_file = package_dir / 'NOTICE.txt'
-        logo_file = package_dir / 'img' / 'security-logo-color-64px.png'
+        logo_file = package_dir / 'img' / 'security-logo-color-64px.svg'
 
-        manifest_file.write_text(yaml.safe_dump(manifest.asdict()))
+        manifest_file.write_text(yaml.safe_dump(manifest.to_dict()))
 
         logo_file.parent.mkdir(parents=True)
         shutil.copyfile(FLEET_PKG_LOGO, logo_file)
@@ -485,7 +485,7 @@ class Package(object):
 
         notice_contents = Path(NOTICE_FILE).read_text()
         readme_text = textwrap.dedent("""
-        # Detection rules
+        # Prebuilt Security Detection Rules
 
         The detection rules package stores the prebuilt security rules for the Elastic Security [detection engine](https://www.elastic.co/guide/en/security/7.13/detection-engine-overview.html).
 
@@ -495,7 +495,7 @@ class Package(object):
 
         ## License Notice
 
-        """) + textwrap.indent(notice_contents, prefix="    ")  # noqa: E501
+        """).lstrip() + textwrap.indent(notice_contents, prefix="    ")  # noqa: E501
 
         readme_file.write_text(readme_text)
         notice_file.write_text(notice_contents)