tsconfig: Set module-related options.

Set `--esModuleInterop` and `--isolatedModules` for consistency with
Babel.  `tsc --init` adds `--esModuleInterop` by default.

Set `--moduleResolution node` so we can find type definitions in
modules that provide them.

Set `--forceConsistentCasingInFileNames`, which seems like a good
idea, and which `tsc --init` will add by default in TypeScript 3.7.

Signed-off-by: Anders Kaseorg <anders@zulipchat.com>

static/js/tsconfig.json

@@ -10,11 +10,15 @@
         "noEmit": true,
         "target": "es5",
         "module": "es6",
+        "esModuleInterop": true,
+        "moduleResolution": "node",
         "sourceMap": true,
 
         /* Strict type-checking */
         "strict": true,
         "strictNullChecks": false,
+        "forceConsistentCasingInFileNames": true,
+        "isolatedModules": true,
 
         /* Additional checks */
         "noUnusedLocals": true,