fix: make isFF checking isomorphic (resolve error on nodejs ReferenceError: navigator is not defined)

[nodkz]

Fix SSR

vpc-admin: [dev] ReferenceError: navigator is not defined
vpc-admin: [dev]     at Object.<anonymous> (/vpc/apps/admin/node_modules/rc-virtual-list/lib/utils/isFirefox.js:7:28)
vpc-admin: [dev]     at Module._compile (internal/modules/cjs/loader.js:778:30)
vpc-admin: [dev]     at Object.Module._extensions..js (internal/modules/cjs/loader.js:789:10)
vpc-admin: [dev]     at Module.load (internal/modules/cjs/loader.js:653:32)
vpc-admin: [dev]     at tryModuleLoad (internal/modules/cjs/loader.js:593:12)
vpc-admin: [dev]     at Function.Module._load (internal/modules/cjs/loader.js:585:3)
vpc-admin: [dev]     at Module.require (internal/modules/cjs/loader.js:692:17)
vpc-admin: [dev]     at require (internal/modules/cjs/helpers.js:25:18)
vpc-admin: [dev]     at Object.<anonymous> (//vpc/apps/admin/node_modules/rc-virtual-list/lib/hooks/useFrameWheel.js:12:41)
vpc-admin: [dev]     at Module._compile (internal/modules/cjs/loader.js:778:30)

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[codecov]

Codecov Report

Merging #50 into master will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master       #50   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           14        14           
  Lines          357       357           
  Branches        64        64           
=========================================
  Hits           357       357           

Impacted Files	Coverage Δ
src/utils/isFirefox.ts	100.00% <100.00%> (ø)

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[zombieJ]

Thanks for PR. We are working on this at same time : )
74525e6