fix: Do not convert ids to dashes in output

BREAKING CHANGE:
Before this change, IDs defined in a GitHub issue template that included a hyphen got converted to dashes for the Action output. This was mainly done to ensure nice-looking output variables. However, this is confusing as discussed in #15 (comment).

fixtures/multiple-paragraphs/expected.json

@@ -1,4 +1,4 @@
 {
-  "textarea_one": "1st paragraph\n\n2nd paragraph",
-  "textarea_two": "1st paragraph\n2nd paragraph"
+  "textarea-one": "1st paragraph\n\n2nd paragraph",
+  "textarea-two": "1st paragraph\n2nd paragraph"
 }

fixtures/readme-example/expected.json

@@ -5,4 +5,4 @@
   "browsers": "Chrome, Safari",
   "never_give_up": true,
   "hot_dog_is_a_sandwich": false
-}
+}

index.js

@@ -44,7 +44,7 @@ async function run(env, eventPayload, fs, core) {
 
   function toKey(str) {
     if (idMapping[str]) {
-      return idMapping[str].replace(/-/g, "_");
+      return idMapping[str];
     }
 
     return str