chore(docs): fix typo (plugion => plugin) in DESIGN_GOALS.md

[styfle]

Summary

This PR fixes a typo in ./compiler/docs/DESIGN_GOALS.md.

I believe plugion should be plugin.

How did you test this change?

Rendered the markdown to html.

[poteto]

Thank you!

[react-sizebot]

Comparing: 50c999e...e6827c7

Critical size changes

Includes critical production bundles, as well as any change greater than 2%:

Name	+/-	Base	Current	+/- gzip	Base gzip	Current gzip
oss-stable/react-dom/cjs/react-dom.production.js	=	6.66 kB	6.66 kB	+0.11%	1.82 kB	1.82 kB
oss-stable/react-dom/cjs/react-dom-client.production.js	=	495.01 kB	495.01 kB	=	88.67 kB	88.68 kB
oss-experimental/react-dom/cjs/react-dom.production.js	=	6.67 kB	6.67 kB	+0.11%	1.83 kB	1.83 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js	=	499.81 kB	499.81 kB	=	89.36 kB	89.36 kB
facebook-www/ReactDOM-prod.classic.js	=	592.16 kB	592.16 kB	=	104.15 kB	104.15 kB
facebook-www/ReactDOM-prod.modern.js	=	568.39 kB	568.39 kB	=	100.55 kB	100.55 kB
test_utils/ReactAllWarnings.js	Deleted	64.26 kB	0.00 kB	Deleted	16.02 kB	0.00 kB

Significant size changes

Includes any change greater than 0.2%:

Expand to show

Name	+/-	Base	Current	+/- gzip	Base gzip	Current gzip
test_utils/ReactAllWarnings.js	Deleted	64.26 kB	0.00 kB	Deleted	16.02 kB	0.00 kB

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