docgen: use github-slugger to generate better slugs

yarn.lock

@@ -3545,6 +3545,11 @@
   resolved "https://registry.npmjs.org/@types/git-url-parse/-/git-url-parse-9.0.0.tgz#aac1315a44fa4ed5a52c3820f6c3c2fb79cbd12d"
   integrity sha512-kA2RxBT/r/ZuDDKwMl+vFWn1Z0lfm1/Ik6Qb91wnSzyzCDa/fkM8gIOq6ruB7xfr37n6Mj5dyivileUVKsidlg==
 
+"@types/github-slugger@^1.3.0":
+  version "1.3.0"
+  resolved "https://registry.npmjs.org/@types/github-slugger/-/github-slugger-1.3.0.tgz#16ab393b30d8ae2a111ac748a015ac05a1fc5524"
+  integrity sha512-J/rMZa7RqiH/rT29TEVZO4nBoDP9XJOjnbbIofg7GQKs4JIduEO3WLpte+6WeUz/TcrXKlY+bM7FYrp8yFB+3g==
+
 "@types/glob@^7.1.1":
   version "7.1.1"
   resolved "https://registry.npmjs.org/@types/glob/-/glob-7.1.1.tgz#aa59a1c6e3fbc421e07ccd31a944c30eba521575"
@@ -7889,6 +7894,11 @@ elliptic@^6.0.0:
     minimalistic-assert "^1.0.0"
     minimalistic-crypto-utils "^1.0.0"
 
+"emoji-regex@>=6.0.0 <=6.1.1":
+  version "6.1.1"
+  resolved "https://registry.npmjs.org/emoji-regex/-/emoji-regex-6.1.1.tgz#c6cd0ec1b0642e2a3c67a1137efc5e796da4f88e"
+  integrity sha1-xs0OwbBkLio8Z6ETfvxeeW2k+I4=
+
 emoji-regex@^7.0.1, emoji-regex@^7.0.2:
   version "7.0.3"
   resolved "https://registry.npmjs.org/emoji-regex/-/emoji-regex-7.0.3.tgz#933a04052860c85e83c122479c4748a8e4c72156"
@@ -9435,6 +9445,13 @@ gitconfiglocal@^1.0.0:
   dependencies:
     ini "^1.3.2"
 
+github-slugger@^1.3.0:
+  version "1.3.0"
+  resolved "https://registry.npmjs.org/github-slugger/-/github-slugger-1.3.0.tgz#9bd0a95c5efdfc46005e82a906ef8e2a059124c9"
+  integrity sha512-gwJScWVNhFYSRDvURk/8yhcFBee6aFjye2a7Lhb2bUyRulpIoek9p0I9Kt7PT67d/nUlZbFu8L9RLiA0woQN8Q==
+  dependencies:
+    emoji-regex ">=6.0.0 <=6.1.1"
+
 glob-base@^0.3.0:
   version "0.3.0"
   resolved "https://registry.npmjs.org/glob-base/-/glob-base-0.3.0.tgz#dbb164f6221b1c0b1ccf82aea328b497df0ea3c4"