Allow browser options while using watch-admin

[erictsangx]

strapi develop --watch-admin   //open the default browser
strapi develop --watch-admin --browser false   //do not open any browser
strapi develop --watch-admin --browser 'google chrome' //open Google Chrome
strapi develop --watch-admin --browser Firefox //open Firefox

[codecov]

Codecov Report

Merging #8054 into master will increase coverage by 0.00%.
The diff coverage is 64.28%.

@@           Coverage Diff           @@
##           master    #8054   +/-   ##
=======================================
  Coverage   32.71%   32.71%           
=======================================
  Files        1194     1194           
  Lines       12965    12970    +5     
  Branches     1279     1280    +1     
=======================================
+ Hits         4241     4243    +2     
- Misses       7884     7887    +3     
  Partials      840      840           

Flag	Coverage Δ
#front	24.80% <0.00%> (-0.01%)	⬇️
#unit	53.88% <100.00%> (+0.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...c/containers/AuthPage/components/Register/index.js	0.00% <ø> (ø)
...trapi-admin/admin/src/containers/AuthPage/index.js	0.00% <0.00%> (ø)
...admin/admin/src/containers/AuthPage/utils/forms.js	0.00% <ø> (ø)
...min/admin/src/containers/ProfilePage/utils/form.js	100.00% <ø> (ø)
.../admin/src/containers/Users/EditPage/utils/form.js	100.00% <ø> (ø)
...-manager/admin/src/components/CustomTable/index.js	0.00% <ø> (ø)
...rc/containers/EditViewDataManagerProvider/index.js	0.00% <0.00%> (ø)
...ugin-upload/admin/src/components/EditForm/index.js	0.00% <0.00%> (ø)
...iners/HomePage/HomePageContent/HomePageSettings.js	0.00% <ø> (ø)
packages/strapi-utils/lib/index.js	100.00% <100.00%> (ø)
... and 1 more

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[soupette]

LGTM!

I have tested and it works correctly! Thanks a lot for your contribution