Relicense Ely Office's own code from AGPL-3.0 to MIT

Applied on top of the released v0.1.6 so the tag says MIT, as main does
(271468d). Bundled engines keep their licences: LibreOffice (MPL-2.0),
Git (GPL-2.0) and MuPDF (AGPL-3.0).

site/src/text.ts

@@ -10,7 +10,7 @@ const en = {
   ElyTree: "Stage lines, commit, read the graph. Git without a terminal.",
   ElyMark: "Markdown as you read it. Math and diagrams in place.",
   offline: "Works with the network off.",
-  open: "Open source, under the AGPL.",
+  open: "Open source, under the MIT licence.",
   local: "Your files stay in your folders.",
   download: "Download",
   platforms: "Out now for macOS, Windows and Linux.",
@@ -48,7 +48,7 @@ const zh: typeof en = {
   ElyTree: "按行暂存、提交、看提交图。不用终端的 Git。",
   ElyMark: "写的就是看到的 Markdown。公式与图表就地显示。",
   offline: "断网照常工作。",
-  open: "开源，AGPL 许可。",
+  open: "开源，MIT 许可。",
   local: "文件留在你自己的文件夹里。",
   download: "下载",
   platforms: "macOS、Windows 与 Linux 版已发布。",