Add category pkg

This supports categories in Write.as / WriteFreely.

Ref T809

go.sum

@@ -15,6 +15,8 @@ github.com/kylemcc/twitter-text-go v0.0.0-20180726194232-7f582f6736ec h1:ZXWuspq
 github.com/kylemcc/twitter-text-go v0.0.0-20180726194232-7f582f6736ec/go.mod h1:voECJzdraJmolzPBgL9Z7ANwXf4oMXaTCsIkdiPpR/g=
 github.com/microcosm-cc/bluemonday v1.0.5 h1:cF59UCKMmmUgqN1baLvqU/B1ZsMori+duLVTLpgiG3w=
 github.com/microcosm-cc/bluemonday v1.0.5/go.mod h1:8iwZnFn2CDDNZ0r6UXhF4xawGvzaqzCRa1n3/lO3W2w=
+github.com/rainycape/unidecode v0.0.0-20150907023854-cb7f23ec59be h1:ta7tUOvsPHVHGom5hKW5VXNc2xZIkfCKP8iaqOyYtUQ=
+github.com/rainycape/unidecode v0.0.0-20150907023854-cb7f23ec59be/go.mod h1:MIDFMn7db1kT65GmV94GzpX9Qdi7N/pQlwb+AN8wh+Q=
 github.com/shurcooL/sanitized_anchor_name v1.0.0 h1:PdmoCO6wvbs+7yrJyMORt4/BmY5IYyJwS/kOiWx8mHo=
 github.com/shurcooL/sanitized_anchor_name v1.0.0/go.mod h1:1NzhyTcUVG4SuEtjjoZeVRXNmyL/1OwPU0+IJeTBvfc=
 github.com/writeas/go-strip-markdown v2.0.1+incompatible h1:IIqxTM5Jr7RzhigcL6FkrCNfXkvbR+Nbu1ls48pXYcw=
@@ -25,6 +27,8 @@ github.com/writeas/openssl-go v1.0.0 h1:YXM1tDXeYOlTyJjoMlYLQH1xOloUimSR1WMF8kjF
 github.com/writeas/openssl-go v1.0.0/go.mod h1:WsKeK5jYl0B5y8ggOmtVjbmb+3rEGqSD25TppjJnETA=
 github.com/writeas/saturday v1.7.1 h1:lYo1EH6CYyrFObQoA9RNWHVlpZA5iYL5Opxo7PYAnZE=
 github.com/writeas/saturday v1.7.1/go.mod h1:ETE1EK6ogxptJpAgUbcJD0prAtX48bSloie80+tvnzQ=
+github.com/writeas/slug v1.2.0 h1:EMQ+cwLiOcA6EtFwUgyw3Ge18x9uflUnOnR6bp/J+/g=
+github.com/writeas/slug v1.2.0/go.mod h1:RE8shOqQP3YhsfsQe0L3RnuejfQ4Mk+JjY5YJQFubfQ=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20200109152110-61a87790db17 h1:nVJ3guKA9qdkEQ3TUdXI9QSINo2CUPM/cySEvw2w8I0=
 golang.org/x/crypto v0.0.0-20200109152110-61a87790db17/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=