Convert frontend code to typescript (#31559)

None of the frontend js/ts files was touched besides these two commands
(edit: no longer true, I touched one file in
https://github.com/go-gitea/gitea/pull/31559/commits/61105d0618e285d97e95044bfb64415f364a4526
because of a deprecation that was not showing before the rename).

`tsc` currently reports 778 errors, so I have disabled it in CI as
planned.

Everything appears to work fine.

1 files changed, 4 insertions, 0 deletions

diff --git a/types.d.ts b/types.d.ts
new file mode 100644
index 0000000000..9348424371
--- /dev/null
+++ b/types.d.ts
@@ -0,0 +1,4 @@
+declare module '*.svg' {
+  const value: string;
+  export default value;
+}