fix!: Make `Loader` object-safe (#83) #201

# to view logs

Job	Run time
no_and_all_features (x86_64-unknown-linux-gnu)	42s
feature_tests (ubuntu, handlebars, walkdir)	45s
no_and_all_features (wasm32-unknown-unknown)	33s
feature_tests (ubuntu, handlebars, ignore)	22s
feature_tests (ubuntu, tera, walkdir)	29s
feature_tests (ubuntu, tera, ignore)	28s
feature_tests (macos, handlebars, walkdir)	20s
feature_tests (macos, handlebars, ignore)	20s
feature_tests (macos, tera, walkdir)	42s
feature_tests (macos, tera, ignore)	25s
feature_tests (windows, handlebars, walkdir)	1m 13s
feature_tests (windows, handlebars, ignore)	1m 2s
feature_tests (windows, tera, walkdir)	1m 42s
feature_tests (windows, tera, ignore)	2m 2s
	11m 5s

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