Disable sourcemap emission by setting "sourceMap": false in tsconfig.base.json.

The published npm packages emit .js.map files that reference ../src/*.ts source files, but src/ is excluded from the published files in each module's package.json. This causes Node.js to warn:

Sourcemap for "..." points to missing source files.

For example, @testcontainers/postgresql references ../src/postgresql-container.ts"

// build/postgresql-container.js.map
{"version":3,"file":"postgresql-container.js","sourceRoot":"","sources":["../src/postgresql-container.ts"],"names":[],"mappings":"..."}

But src/ does not exist:

Since the source files are never published, the sourcemaps are not useful to consumers and should not be emitted. (Could also allow src/ in packages instead of disabling sourcemap generation.)