[routing] Support custom HTTP methods

[tipsy]

Closes #2331

[codecov]

Codecov Report

❌ Patch coverage is 89.36170% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.41%. Comparing base (7a14a71) to head (6958605).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...lin/src/main/java/io/javalin/http/HandlerType.java	94.87%	0 Missing and 2 partials ⚠️
...main/java/io/javalin/router/matcher/PathMatcher.kt	66.66%	0 Missing and 2 partials ⚠️
javalin/src/main/java/io/javalin/http/Context.kt	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #2478      +/-   ##
============================================
+ Coverage     86.39%   86.41%   +0.02%     
- Complexity     1447     1462      +15     
============================================
  Files           149      149              
  Lines          4646     4668      +22     
  Branches        489      490       +1     
============================================
+ Hits           4014     4034      +20     
  Misses          409      409              
- Partials        223      225       +2     

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