feat(storage): expose purgeCache

[mandarini]

Authored by @mansueli
Moved from here: supabase/storage-js#229

What kind of change does this PR introduce?

The goal is to expose the purgeCache operation from the API to the client libraries.

 "/cdn/{bucketName}/{wildcard}": { "delete": { "summary": "Purge cache for an object", "tags": [ "object" ], "parameters": [ { "schema": { "type": "string" }, "example": "avatars", "in": "path", "name": "bucketName", "required": true }, { "schema": { "type": "string" }, "example": "folder/cat.png", "in": "path", "name": "*", "required": true }, { "schema": { "type": "string" }, "example": "Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJzdXBhYmFzZS1kZW1vIiwicm9sZSI6ImFub24ifQ.625_WdcF3KHqz5amU0x2X5WWHP-OEs_4qj0ssLNHzTs", "in": "header", "name": "authorization", "required": true } ], "responses": { "200": { "description": "Successful response", "content": { "application/json": { "schema": { "description": "Successful response", "type": "object", "properties": { "message": { "type": "string", "examples": [ "success" ] } } } } } }, "4XX": { "description": "Error response", "content": { "application/json": { "schema": { "description": "Error response", "$ref": "#/components/schemas/def-1" } } } } } } }, 

What is the current behavior?

There's no support this in the client libraries.

What is the new behavior?

The goal is to allow this to be exposed in the supabase-js client e.g:

storage.from(BUCKET_ID).purgeCache('test.png') 

[coveralls]

coverage: 95.455% (+13.0%) from 82.5%
when pulling c33f0ac on feat/expose-purgeCache
into 2d0bd77 on master.