chore: editorconfig matching existing code format styles

An editor config has been written that matches existing indentation and
formatting used by this project, which should extend the courtesy of
intended tab use to other editors like NeoVim which are often conigured
to adhere to `.editorconfig` by default.

As part of this change, the official EditorConfig extension has been
added to VSCode recommendations, which should additionally enable
Code-like editors to additionally adhere to the rules of other files
like json and markdown which are the only types that deviate from
Cadence's global default.

.editorconfig

@@ -0,0 +1,16 @@
+root = true
+
+[*]
+indent_style = tab
+tab_width = 3
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[*.json]
+indent_style = space
+indent_size = 2
+
+[*.md]
+trim_trailing_whitespace = false

.vscode/extensions.json

@@ -0,0 +1,5 @@
+{
+	"recommendations": [
+		"editorconfig.editorconfig"
+	]
+}