Enable tsc alwaysStrict, strictBindCallApply, noImplicitThis (#9600)

* Enable tsc alwaysStrict

* Enable tsc strictBindCallApply

* Enable tsc noImplicitThis

* Add d.ts

* Improve types

* Add ?

* Increase coverage

* Improve coverage

src/utils/MegolmExportEncryption.ts

@@ -356,7 +356,7 @@ function packMegolmKeyFile(data: Uint8Array): ArrayBuffer {
 function encodeBase64(uint8Array: Uint8Array): string {
     // Misinterpt the Uint8Array as Latin-1.
     // window.btoa expects a unicode string with codepoints in the range 0-255.
-    const latin1String = String.fromCharCode.apply(null, uint8Array);
+    const latin1String = String.fromCharCode.apply(null, Array.from(uint8Array));
     // Use the builtin base64 encoder.
     return window.btoa(latin1String);
 }