[SM-1399] Update the README for Windows on ARM (#942)

## 🎟️ Tracking

https://bitwarden.atlassian.net/browse/SM-1399

## 📔 Objective

Just `cargo build` is not sufficient for building the SDK on Windows on
ARM. We should add clarity to what is required so that `cargo build`
will run successfully.

Python is required. Clang is also required for
[ring](https://crates.io/crates/ring) (more info
[here](https://github.com/briansmith/ring/blob/main/BUILDING.md)).

## ⏰ Reminders before review

- Contributor guidelines followed
- All formatters and local linters executed and passed
- Written new unit and / or integration tests where applicable
- Protected functional changes with optionality (feature flags)
- Used internationalization (i18n) for all UI strings
- CI builds passed
- Communicated to DevOps any deployment requirements
- Updated any necessary documentation (Confluence, contributing docs) or
informed the documentation
  team

## 🦮 Reviewer guidelines

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- 👍 (`:+1:`) or similar for great changes
- 📝 (`:memo:`) or ℹ️ (`:information_source:`) for notes or general info
- ❓ (`:question:`) for questions
- 🤔 (`:thinking:`) or 💭 (`:thought_balloon:`) for more open inquiry
that's not quite a confirmed
  issue and could potentially benefit from discussion
- 🎨 (`:art:`) for suggestions / improvements
- ❌ (`:x:`) or ⚠️ (`:warning:`) for more significant problems or
concerns needing attention
- 🌱 (`:seedling:`) or ♻️ (`:recycle:`) for future improvements or
indications of technical debt
- ⛏ (`:pick:`) for minor or nitpick changes

README.md

@@ -20,10 +20,21 @@ are currently open as well as what it's like to work at Bitwarden.
 
 ## Getting Started
 
+### Linux / Mac / Windows
+
 ```bash
 cargo build
 ```
 
+### Windows on ARM
+
+To build, you will need the following in your PATH:
+
+- [Python](https://www.python.org)
+- [Clang](https://clang.llvm.org)
+  - We recommend installing this via the
+    [Visual Studio Build Tools](https://visualstudio.microsoft.com/downloads/#build-tools-for-visual-studio-2022)
+
 ## Crates
 
 The project is structured as a monorepo using cargo workspaces. Some of the more noteworthy crates