Add flexbox error logging for native

[necolas]

Print an error message if flex properties are used on native without the required "display:flex" style. This should help prevent layout divergence between native and web for native-first development.

[github-actions]

workflow: benchmarks/size

Comparison of minified (terser) and compressed (brotli) size results, measured in bytes. Smaller is better.

Results	Base	Patch	Ratio
react-strict-dom/dist/dom/index.js
· compressed	2,514	2,514	1.00
· minified	8,691	8,691	1.00
react-strict-dom/dist/dom/runtime.js
· compressed	855	855	1.00
· minified	2,435	2,435	1.00
react-strict-dom/dist/native/index.js
· compressed	16,021	16,098	1.00	+
· minified	59,998	60,314	1.01	+

[github-actions]

workflow: benchmarks/perf (native)

Comparison of performance test results, measured in operations per second. Larger is better.

Results	Base	Patch	Ratio
css.create
· small	1,141,429	1,140,285	1.00	-
· small with units	422,678	431,199	1.02	+
· small with variables	671,357	646,950	0.96	-
· several small	313,217	318,633	1.02	+
· large	202,455	206,870	1.02	+
· large with polyfills	142,544	145,055	1.02	+
· complex	97,468	98,586	1.01	+
· unsupported	213,520	216,181	1.01	+
css.createTheme
· simple theme	224,416	224,393	1.00	-
· polyfill theme	210,661	210,865	1.00	+
css.props
· small	280,373	282,335	1.01	+
· small with units	221,752	223,027	1.01	+
· small with variables	112,310	113,710	1.01	+
· small with variables of units	78,682	79,517	1.01	+
· large	120,252	120,614	1.00	+
· large with polyfills	41,150	41,817	1.02	+
· complex	25,279	25,482	1.01	+
· unsupported	178,640	180,178	1.01	+
· simple merge	184,416	185,557	1.01	+
· wide merge	19,223	19,355	1.01	+
· deep merge	18,795	19,011	1.01	+
· themed merge	36,844	36,848	1.00	+