Add static variable for MiddlewareUniversalName.

[mlajx]

Hi,

I am working on a project that uses sharp as the dashboard.

I need to use it both to login to the 'central' and 'tenants', and when I found the solution (use the Feature UniversalRoutes), I noticed that Sharp does not publish its route, so I found another way to solve the problem, which would be to extend the UniversalRoutes class and then change universal to sharp_web (middleware that sharp uses on all of its dashboard routes), so that I don't have to add the 'universal' class to the routes (changing something in the vendor dir or copying all the sharp routes to laravel app).

Thinking about it, I found it interesting to do this PR by creating a public static variable, making it possible to extend the class and then just change the middleware name to something specific (in case you happen to fall into the same problem with someone).

Sorry about my english, isn't my first language.

[codecov]

Codecov Report

Merging #581 (65aecb9) into 3.x (04193cc) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##                3.x     #581   +/-   ##
=========================================
  Coverage     86.94%   86.94%           
  Complexity      366      366           
=========================================
  Files           103      103           
  Lines          1088     1088           
=========================================
  Hits            946      946           
  Misses          142      142           

Impacted Files	Coverage Δ	Complexity Δ
src/Features/UniversalRoutes.php	92.85% <100.00%> (ø)	9.00 <0.00> (ø)

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[stancl]

You could solve this by just extending the class and registering the feature yourself, but this is a simple change and I agree that this makes it more consistent with the rest of the codebase that allows configuration through static properties.

The feature itself is fine, but please make these few changes.

Thanks!

[stancl]

Thanks! Released as 3.4.1.