chore: add harfbuzz to Homebrew installation in README.md (#57)

* chore: add harfbuzz to Homebrew installation in README.md

* Update future work
	ref: #57 (comment)

README.md

@@ -31,7 +31,7 @@ scoop install git python llvm cmake curl
 - Install [Homebrew](https://brew.sh/) and then install other tools:
 
 ```sh
-brew install cmake pkg-config
+brew install cmake pkg-config harfbuzz
 ```
 
 ### Linux
@@ -69,5 +69,6 @@ Nightly releases built with CrabNebula Cloud can be found at [releases](https://
 ## Future Work
 
 - Add more window and servo features to make it feel more like a general web browser.
-- Improve  development experience.
+- Improve development experience.
 - Multi webviews and multi browsing contexts in the same window.
+- Enable `Gstreamer` feature and remove `brew install harfbuzz` in README.