Signup: add a link to the terms of service.

Fixes #188.

src/SignupPage.tsx

@@ -246,7 +246,7 @@ export default function SignupPage() {
         </Alert>
 
         <p style={styles.infoAlert}>
-          You can also signup using <ExternalLink href={C.getApps}>any of the apps</ExternalLink>.
+          By signing up you agree to our <ExternalLink href={C.terms}>terms of service</ExternalLink>.
         </p>
 
         <div style={styles.submit}>

src/constants/index.ts

@@ -7,6 +7,7 @@ export const homePage = "https://www.etesync.com/";
 export const faq = homePage + "faq/";
 export const pricing = homePage + "pricing/";
 export const getApps = homePage + "get-apps/";
+export const terms = homePage + "tos/";
 export const sourceCode = "https://github.com/etesync/etesync-web";
 export const reportIssue = sourceCode + "/issues";