Improve bundle size of script for browser to be smaller

[yhatt]

We've improved bundle size of script for browser to be smaller.

• Split up attribute constants of fitting feature to prevent bundling unnecessary functions.
• Update @marp-team/marpit-svg-polyfill to v1.1.0. It has already became JS size about 5x smaller.

Build	Original	Improved	Difference
Build for Brower (browser.js)	8071 bytes (8.1KB)	1714 bytes (1.7KB)	-6357 bytes (-6.4KB)
Build for CommonJS (browser.cjs.js)	7468 bytes (7.5KB)	1594 bytes (1.6KB)	-5874 bytes (-5.9KB)