Update README.md

Author: lukepistrol

README.md

@@ -1,3 +1,73 @@
 # CodeEditSymbols
 
-A description of this package.
+A package containing all custom assets for CodeEdit. These are mostly custom [SF Symbols](https://developer.apple.com/design/human-interface-guidelines/sf-symbols/overview/#creating-custom-symbols).
+
+## How to use
+
+### `NSImage`:
+
+```swift
+import CodeEditSymbols
+
+let nsImage = NSImage.symbol(named: "name_of_the_symbol")
+```
+
+### `Image`:
+
+```swift
+import CodeEditSymbols
+
+let image = Image(symbol: "name_of_the_symbol")
+```
+
+## Creating a new Asset
+
+To create a new asset, follow the guide on [Apple's developer website](https://developer.apple.com/documentation/uikit/uiimage/creating_custom_symbol_images_for_your_app).
+
+Add the `.svg` you exported from `SF Symbols.app` to the `Symbols.xcassets` catalog.
+
+> **Important:** Make sure your symbol looks great in every font weight.
+
+## Tests
+
+Also include snapshot tests for each symbol for `Image` as well as `NSImage`:
+
+### `NSImage`:
+
+```swift
+// MARK: YOUR_SYMBOL_NAME
+
+func testCreateNSImageYourSymbolName() {
+    let image = NSImage.symbol(named: "your_symbol_name")
+    let view = NSImageView(image: image)
+    assertSnapshot(matching: view, as: .image)
+}
+```
+
+### `Image`:
+
+```swift
+// MARK: YOUR_SYMBOL_NAME
+
+func testCreateImageYourSymbolName() {
+    let image = Image(symbol: "your_symbol_name")
+    let view: NSView = NSHostingController(rootView: image).view
+    assertSnapshot(matching: view, as: .image(size: view.intrinsicContentSize))
+}
+```
+
+## Variants
+
+Keep different variants of a symbol in the same parent folder and name them appropriately (see Apple's own symbols for reference).
+
+You might have a symbol called `lock` and one where the symbol is inside a square where you would call that file `lock.square`. Also keep in mind to also provide a `.fill` variant if appropriate (`lock.fill`, `lock.square.fill`)
+
+### Example of a `.fill` Variant
+
+<img width="256" alt="Screen Shot 2022-04-18 at 00 29 57" src="https://user-images.githubusercontent.com/9460130/163734754-9eff9671-bb19-46de-92b0-c4c0de27c23b.png">
+
+## Annotate the Symbol
+
+As of version 3 of `SF Symbols` it is possible to create `multi-color`, `hierarchical` and `palette` annotations inside the `SF Symbols.app`. Be sure to annotate it accordingly if appropriate.
+
+<img width="266" alt="Screen Shot 2022-04-18 at 00 40 26" src="https://user-images.githubusercontent.com/9460130/163734926-d4da422a-d7f0-4b93-a05b-3d1700c1b97c.png">