Enable sourcemaps (#278)

Enables the generation of sourcemap files, which allow debuggers and
other tools to display the original TypeScript source code when actually
working with the emitted JavaScript files. This should provide better
introspection of zarrita code.

Author: manzt

.changeset/thick-owls-swim.md

@@ -0,0 +1,7 @@
+---
+"@zarrita/ndarray": patch
+"@zarrita/storage": patch
+"zarrita": patch
+---
+
+Emit and publish [sourcemap files](http://web.dev/articles/source-maps)

tsconfig.json

@@ -9,6 +9,7 @@
 		"verbatimModuleSyntax": true,
 		"isolatedModules": true,
 		"declaration": true,
+		"sourceMap": true,
 		/* Linting */
 		"strict": true,
 		"noUnusedLocals": true,