Add installation instructions

docs/installation.md

@@ -12,4 +12,41 @@ LangCheck works with Python 3.8 or higher.
 Model files are lazily downloaded the first time you run a metric function. For example, the first time you run the ``langcheck.metrics.sentiment()`` function, LangCheck will automatically download the Twitter-roBERTa-base model.
 :::
 
-To install LangCheck directly from the repository source, see [the Contributing page](contributing.md).
+To install LangCheck from source, see [the Contributing page](contributing.md).
+
+## Installation FAQ
+
+Depending on your environment, you might need to install additional system libraries for `pip install langcheck` to work.
+
+If you have any problems installing LangCheck, please check the FAQ below or [open an issue on GitHub](https://github.com/citadel-ai/langcheck/issues).
+
+### 1. Installing LangCheck with Python 3.12
+
+As of February 2024, one of LangCheck's Japanese dependencies, [`fugashi`](https://github.com/polm/fugashi), doesn't provide wheels for Python 3.12, so you'll need to first install MeCab for pip to successfully build `fugashi`.
+
+**Installing MeCab on Linux (Debian/Ubuntu)**
+
+```bash
+sudo apt-get update
+sudo apt-get install -y mecab libmecab-dev mecab-ipadic-utf8
+```
+
+**Installing MeCab on macOS**
+
+```bash
+brew install mecab
+```
+
+**Installing MeCab on Windows**
+
+We haven't tested LangCheck on Windows with Python 3.12, but it may work if you install MeCab with [the official installer](https://taku910.github.io/mecab/#install).
+
+### 2. The error message `command 'gcc' failed`
+
+As of February 2024, one of LangCheck's Japanese dependencies, [`dartsclone`](https://github.com/s-yata/darts-clone), doesn't provide wheels for Python 3.10+. You'll need to have `gcc` installed for pip to successfully build `dartsclone`.
+
+Most systems already have `gcc` installed, with the exception of "slim" Docker images such as [`python:3.11-slim-buster`](https://hub.docker.com/_/python). If you're using this image, you can:
+
+1. Use `python:3.11-buster` instead of `python:3.11-slim-buster`, which includes gcc.
+1. Run `apt update && apt install build-essential -y` (e.g. in your Dockerfile) to install gcc.
+