[O] i18n placeholders

AquaNet/src/libs/i18n.ts

@@ -1,6 +1,9 @@
 
 const EN_REF = {
   'back': 'Back',
+  'email': 'Email',
+  'password': 'Password',
+  'username': 'Username',
   'welcome.btn-login': 'Log in',
   'welcome.btn-signup': 'Sign up',
   'welcome.email-password-missing': 'Email and password are required',
@@ -21,6 +24,9 @@ const msgs: { [index: string]: typeof EN_REF } = {
   en: EN_REF,
   zh: {
     'back': '返回',
+    'email': '邮箱',
+    'password': '密码',
+    'username': '用户名',
     'welcome.btn-login': '登录',
     'welcome.btn-signup': '注册',
     'welcome.email-password-missing': '邮箱和密码必须填哦',

AquaNet/src/pages/Welcome.svelte

@@ -120,10 +120,10 @@
           <span>{t('back')}</span>
         </div>
         {#if isSignup}
-          <input type="text" placeholder="Username" bind:value={username}>
+          <input type="text" placeholder={t('username')} bind:value={username}>
         {/if}
-        <input type="email" placeholder="Email" bind:value={email}>
+        <input type="email" placeholder={t('email')} bind:value={email}>
-        <input type="password" placeholder="Password" bind:value={password}>
+        <input type="password" placeholder={t('password')} bind:value={password}>
         <button on:click={submit}>
           {#if submitting}
             <Icon icon="line-md:loading-twotone-loop"/>