feat: export new RELEASE_TYPES constant

Which will help library consumers better integrate semver into their apps.

Possible usecases of consuming this constant:

- Automatically show a dropdown of available release types that conform to the semver spec
- Validate user inputs where a release type is expected

index.js

@@ -83,6 +83,7 @@ module.exports = {
   src: internalRe.src,
   tokens: internalRe.t,
   SEMVER_SPEC_VERSION: constants.SEMVER_SPEC_VERSION,
+  RELEASE_TYPES: constants.RELEASE_TYPES,
   compareIdentifiers: identifiers.compareIdentifiers,
   rcompareIdentifiers: identifiers.rcompareIdentifiers,
 }

internal/constants.js

@@ -9,9 +9,20 @@ const MAX_SAFE_INTEGER = Number.MAX_SAFE_INTEGER ||
 // Max safe segment length for coercion.
 const MAX_SAFE_COMPONENT_LENGTH = 16
 
+const RELEASE_TYPES = [
+  'major',
+  'premajor',
+  'minor',
+  'preminor',
+  'patch',
+  'prepatch',
+  'prerelease',
+]
+
 module.exports = {
-  SEMVER_SPEC_VERSION,
   MAX_LENGTH,
-  MAX_SAFE_INTEGER,
   MAX_SAFE_COMPONENT_LENGTH,
+  MAX_SAFE_INTEGER,
+  RELEASE_TYPES,
+  SEMVER_SPEC_VERSION,
 }