Add GH_TOKEN variable for semantic-release

[landonreed]

Checklist

• [x] Appropriate branch selected (all PRs must first be merged to dev before they can be merged to master)
• [x] Any modified or new methods or classes have helpful JavaDoc and code is thoroughly commented
• [x] The description lists all applicable issues this PR seeks to resolve
• [x] The description lists any configuration setting(s) that differ from the default settings
• [x] All tests and CI builds passing

Description

fix #306 by adding the GH_TOKEN env variable to the release step.

[codecov-io]

Codecov Report

Merging #307 (c739f20) into dev (6b33a8c) will decrease coverage by 0.02%. The diff coverage is n/a.

@@             Coverage Diff              @@
##                dev     #307      +/-   ##
============================================
- Coverage     66.17%   66.14%   -0.03%     
  Complexity      926      926              
============================================
  Files           136      136              
  Lines          6838     6838              
  Branches        816      816              
============================================
- Hits           4525     4523       -2     
- Misses         2019     2022       +3     
+ Partials        294      293       -1     

Impacted Files	Coverage Δ	Complexity Δ
src/main/java/com/conveyal/gtfs/PatternFinder.java	85.22% <0.00%> (-2.28%)	20.00% <0.00%> (ø%)

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