feat: upgrading future development and testing of this plugin exclusively to Serverless v3 (#284)

Upgrading this to Serverless v3. I haven't changed any behavior or code to do this so I expect this will continue to work with Serverless v2, but I do not plan to test against Serverless v2 going forward. The tests have been using Serverless v3 for some time now per https://github.com/activescott/serverless-aws-static-file-handler/blame/c779fdd93662784c1a7b651057764d64734b13fb/examples/serverless-offline/package.json#L16 so this should be of negligible impact.

If you want to use a version before this set of changes you can use v4.0.4.

So why? The serverless community is focused on the v3 version at this point and Serverless v2 brings along a few vulnerability warnings due to it's outdated dependencies that I'd prefer to not ignore.

Author: activescott

examples/basic/package.json

@@ -14,7 +14,7 @@
     "dev-unlink": "npm rm serverless-aws-static-file-handler ; npm add serverless-aws-static-file-handler@>=3.0.2-beta.1"
   },
   "devDependencies": {
-    "serverless": "^3.1.0"
+    "serverless": "^3.37.0"
   },
   "dependencies": {
     "serverless-aws-static-file-handler": ">=3.0.2-beta.1"

examples/serverless-offline/package.json

@@ -13,8 +13,8 @@
     "dev-unlink": "npm i"
   },
   "devDependencies": {
-    "serverless": "^3.1.1",
-    "serverless-offline": "^13.2.0"
+    "serverless": "^3.37.0",
+    "serverless-offline": "^13.3.0"
   },
   "dependencies": {
     "serverless-aws-static-file-handler": ">=3.0.2-beta.1"