build: Initial linting setup (#1560)

* sets up linting config and runs `yarn lint --fix` once, so that all changes will show up correctly in future PRs.

* Note that there are still a lot of linter errors.

.vscode/settings.json

@@ -0,0 +1,35 @@
+{
+    "editor.tabSize": 2,
+    "[javascript]": {
+        "editor.defaultFormatter": "esbenp.prettier-vscode",
+        "editor.formatOnSave": true
+    },
+    "[javascriptreact]": {
+        "editor.defaultFormatter": "esbenp.prettier-vscode",
+        "editor.formatOnSave": true
+    },
+    "[typescript]": {
+        "editor.defaultFormatter": "esbenp.prettier-vscode",
+        "editor.formatOnSave": true
+    },
+    "[typescriptreact]": {
+        "editor.defaultFormatter": "esbenp.prettier-vscode",
+        "editor.formatOnSave": true
+    },
+    "eslint.alwaysShowStatus": true,
+    "eslint.lintTask.enable": true,
+    "eslint.codeAction.showDocumentation": {
+        "enable": true
+    },
+    "editor.codeActionsOnSave": {
+        "source.fixAll.eslint": true
+    },
+    "files.insertFinalNewline": true,
+    "files.trimFinalNewlines": true,
+    "files.trimTrailingWhitespace": true,
+    "files.watcherExclude": {
+        "**/.git/objects/**": true,
+        "**/.git/subtree-cache/**": true,
+        "**/.hg/store/**": true
+    },
+}