feat(Value): Control key order

[epage]

Fixes #159

[epage]

For reference, base bench

running 6 tests
test bench_parse_template  ... bench:      22,776 ns/iter (+/- 1,571)
test bench_parse_text      ... bench:         841 ns/iter (+/- 55)
test bench_parse_variable  ... bench:       2,861 ns/iter (+/- 220)
test bench_render_template ... bench:       7,002 ns/iter (+/- 562)
test bench_render_text     ... bench:         440 ns/iter (+/- 32)
test bench_render_variable ... bench:       6,389 ns/iter (+/- 541)

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With object_sorted (YMMV)

running 6 tests
test bench_parse_template  ... bench:      22,772 ns/iter (+/- 2,619)
test bench_parse_text      ... bench:         820 ns/iter (+/- 62)
test bench_parse_variable  ... bench:       2,883 ns/iter (+/- 490)
test bench_render_template ... bench:       6,474 ns/iter (+/- 625)
test bench_render_text     ... bench:         511 ns/iter (+/- 46)
test bench_render_variable ... bench:       6,116 ns/iter (+/- 322