add eslint and prettier configuration

.eslintignore

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+packages/*/node_modules/*
+packages/backend/mongodb/

.eslintrc

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+{
+  "parser": "@typescript-eslint/parser",
+  "extends": [
+    "eslint:recommended",
+    "plugin:@typescript-eslint/recommended",
+    "prettier/@typescript-eslint",
+    "plugin:prettier/recommended"
+  ],
+  "plugins": ["@typescript-eslint"],
+  "parserOptions": {
+    "ecmaVersion": 2018,
+    "sourceType": "module",
+    "project": "./tsconfig.lint.json"
+  },
+  "env": {
+    "browser": true,
+    "node": true,
+    "es6": true
+  },
+  "overrides": [
+    {
+      "files": ["*.ts", "*.d.ts"],
+      "rules": {
+        "max-len": [
+          "error",
+          {
+            "code": 120,
+            "ignoreUrls": true
+          }
+        ],
+        "camelcase": "off",
+        "@typescript-eslint/interface-name-prefix": "off",
+        "@typescript-eslint/no-explicit-any": "off",
+        "@typescript-eslint/camelcase": "off"
+      }
+    }
+  ]
+}

.prettierrc

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+{
+  "printWidth": 120,
+  "singleQuote": true,
+  "trailingComma": "all"
+}