Convert files to typescript

The change converts the following files to typescript:

* elements/core/gr-main-header/gr-main-header.ts

Change-Id: I4836d9a65cb00c522f6fdabda26e35b3363ab224
diff --git a/polygerrit-ui/app/constants/constants.ts b/polygerrit-ui/app/constants/constants.ts
index 5a925ff..8e8eaf3 100644
--- a/polygerrit-ui/app/constants/constants.ts
+++ b/polygerrit-ui/app/constants/constants.ts
@@ -341,3 +341,20 @@
   OWNER_REVIEWERS = 'OWNER_REVIEWERS',
   ALL = 'ALL',
 }
+
+/**
+ * The authentication type that is configured on the server.
+ * https://gerrit-review.googlesource.com/Documentation/rest-api-config.html#auth-info
+ */
+export enum AuthType {
+  OPENID = 'OPENID',
+  OPENID_SSO = 'OPENID_SSO',
+  OAUTH = 'OAUTH',
+  HTTP = 'HTTP',
+  HTTP_LDAP = 'HTTP_LDAP',
+  CLIENT_SSL_CERT_LDAP = 'CLIENT_SSL_CERT_LDAP',
+  LDAP = 'LDAP',
+  LDAP_BIND = 'LDAP_BIND',
+  CUSTOM_EXTENSION = 'CUSTOM_EXTENSION',
+  DEVELOPMENT_BECOME_ANY_ACCOUNT = 'DEVELOPMENT_BECOME_ANY_ACCOUNT',
+}