Open the composer full screen, as a setting (#401) (#404)

Settings > General > Composing has a new switch, "Open the composer full
screen". With it on, every new composer, whether a new message, reply,
forward or reopened draft, starts maximized. Restore still shrinks it to
a window. A draft put back after an undone or failed send keeps the size
it had. It's off by default, and on a phone, where the composer already
fills the screen, it changes nothing.

One new string, translated in all nine catalogs. The count falling back
to English stays at 16 in every language.

Fixes #401

web/src/locales/zh-Hans.ts

@@ -748,6 +748,7 @@ export const catalog: Catalog = {
     "Attachment reminder": "附件提醒",
     "Warn when the message mentions an attachment but none is attached.": "邮件提到附件但未添加时提醒。",
     "Spell check while typing": "输入时检查拼写",
+    "Open the composer full screen": "全屏写邮件",
     "Confirm before deleting": "删除前确认",
     "Show message snippets": "显示邮件摘要",
     "Preview the first line of each message in the list.": "在列表中显示每封邮件的首行。",