Lazy ERC20 watcher (#11)

* Storage mapping utils.

* Resolver factories.

* Get ERC20 balance from upstream ipld-eth-server slot.

* Get ERC20 allowance from storage slot.

* Parse ERC20 events from block events.

* Cache GQL requests in leveldb.

* Refactor fetch/cache from upstream into eth-loader class.

* Refactoring.

* Refactor eth-client, extract cache class.

* Cache config settings.

* Debug logs.

* Rename server to watcher.

* Start local server by default.

* Split into multiple packages.

* eth-client API methods.

* Update docs.

packages/cache/package.json

@@ -0,0 +1,45 @@
+{
+    "name": "@vulcanize/cache",
+    "version": "0.1.0",
+    "description": "Generic object cache",
+    "private": true,
+    "main": "index.ts",
+    "scripts": {
+      "test": "mocha -r ts-node/register src/**/*.spec.ts"
+    },
+    "repository": {
+      "type": "git",
+      "url": "git+https://github.com/vulcanize/erc20-watcher.git"
+    },
+    "author": "",
+    "license": "UNLICENSED",
+    "bugs": {
+      "url": "https://github.com/vulcanize/erc20-watcher/issues"
+    },
+    "homepage": "https://github.com/vulcanize/erc20-watcher#readme",
+    "dependencies": {
+      "@types/lodash": "^4.14.168",
+      "apollo-type-bigint": "^0.1.3",
+      "canonical-json": "^0.0.4",
+      "debug": "^4.3.1",
+      "ethers": "^5.2.0",
+      "express": "^4.17.1",
+      "express-graphql": "^0.12.0",
+      "fs-extra": "^10.0.0",
+      "graphql": "^15.5.0",
+      "graphql-import-node": "^0.0.4",
+      "graphql-request": "^3.4.0",
+      "graphql-tools": "^7.0.4",
+      "left-pad": "^1.3.0",
+      "level": "^7.0.0",
+      "lodash": "^4.17.21",
+      "toml": "^3.0.0",
+      "yargs": "^17.0.1"
+    },
+    "devDependencies": {
+      "@types/express": "^4.17.11",
+      "@types/yargs": "^17.0.0",
+      "nodemon": "^2.0.7",
+      "ts-node": "^10.0.0"
+    }
+  }