ci: add spell checking (#4148)

Adds [typos](https://github.com/crate-ci/typos) as a CI check and
pre-commit hook, the same way Lance does it, so misspellings like the
ones fixed in #4146 get caught automatically going forward.

This also fixes the misspellings `typos` found across the repo (Rust,
Python, TypeScript source, comments, and generated docs), and adds a
small `.typos.toml` with `extend-words` entries for terms that are
correct but look like typos: `AKS` (Azure Kubernetes Service), `RabitQ`
(a real quantization algorithm name), `mmaped` (the actual name of a
`candle-core` API we call), and `Writeable` (from Python's
`_typeshed.WriteableBuffer`). Third-party license files are excluded.

Fixes #4147

Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>

.github/workflows/typos.yml

@@ -0,0 +1,20 @@
+name: Typo checker
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+
+permissions:
+  contents: read
+
+jobs:
+  run:
+    name: Spell Check with Typos
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out code
+        uses: actions/checkout@v6
+
+      - name: Check spelling of the entire repository
+        uses: crate-ci/typos@6802cc60d4e7f78b9d5454f6cf3935c042d5e1e3 # v1.26.0