fix: migrate segment subscribers + typescript support (#5904)

Fixes #6068.

**What**

- Uses new Subscriber API.
- Adds support for typescript files in Segment plugin.
- Adds a peerDependency on @medusajs/medusa for the version that introduced new Subscriber API.

yarn.lock

@@ -37380,27 +37380,18 @@ __metadata:
   version: 0.0.0-use.local
   resolution: "medusa-plugin-segment@workspace:packages/medusa-plugin-segment"
   dependencies:
-    "@babel/cli": ^7.7.5
-    "@babel/core": ^7.7.5
-    "@babel/node": ^7.7.4
-    "@babel/plugin-proposal-class-properties": ^7.7.4
-    "@babel/plugin-transform-classes": ^7.9.5
-    "@babel/plugin-transform-instanceof": ^7.8.3
-    "@babel/plugin-transform-runtime": ^7.7.6
-    "@babel/preset-env": ^7.7.5
-    "@babel/register": ^7.7.4
-    "@babel/runtime": ^7.9.6
     analytics-node: ^3.4.0-beta.1
     axios: ^0.19.2
-    body-parser: ^1.19.0
     cross-env: ^5.2.1
     eslint: ^6.8.0
-    express: ^4.17.1
     jest: ^25.5.4
     medusa-core-utils: ^1.2.0
     medusa-interfaces: ^1.3.7
     medusa-test-utils: ^1.1.40
+    rimraf: ^5.0.1
+    typescript: ^4.9.5
   peerDependencies:
+    "@medusajs/medusa": ">= 1.18.0 < 2"
     medusa-interfaces: ^1.3.7
   languageName: unknown
   linkType: soft