test: add tests for utils in devtools-vite

[liangmiQwQ]

Added some tests in package/devtools-vite/src/app/utils/__tests__/

It helped me to find and fix #75 #73

% Coverage report from v8

Before:

File	Stmts	Branch	Funcs	Lines
All Files	1.74	40.28	33.67	1.74
devtools-vite/src/app/utils	21.32	79.41	62.06	21.32
cache.ts	78.12	89.65	70.83	78.12
color.ts	0	0	0	0
filepath.ts	0	0	0	0
format.ts	0	100	100	0
icon.ts	0	0	0	0
is.ts	0	0	0	0

After:

File	Stmts	Branch	Funcs	Lines
All Files	4.64	53.95	39.61	4.64
devtools-vite/src/app/utils	93.39	90.19	85	93.39
cache.ts	87.5	87.5	76	87.5
color.ts	86.95	90.9	100	86.95
filepath.ts	95.52	96.66	100	95.52
format.ts	87.5	76.47	100	87.5
icon.ts	100	100	100	100
is.ts	100	100	100	100