add .clang-format file, add extension recommendation

.clang-format

+---
+BasedOnStyle: LLVM
+ColumnLimit: 120
+IndentWidth: 4
+TabWidth: 4
+UseTab: ForIndentation
+AlignEscapedNewlines: DontAlign
+AllowShortFunctionsOnASingleLine: Inline
+AlwaysBreakTemplateDeclarations: Yes
+BreakBeforeBinaryOperators: NonAssignment
+BreakBeforeBraces: Custom
+BraceWrapping:
+  AfterFunction: true

.vscode/extensions.json

+{
+  // See http://go.microsoft.com/fwlink/?LinkId=827846
+  // for the documentation about the extensions.json format
+  "recommendations": ["platformio.platformio-ide", "xaver.clang-format"]
+}

.vscode/tasks.json

+{
+  "version": "0.1.0",
+  "tasks": [
+    {
+      "taskName": "clang-format-everything",
+      "command": "clang-format",
+      "args": ["-i", "*"],
+      "isShellCommand": true,
+      "isBackground": true
+    }
+  ]
+}