devops: Add build task & notes to taskfile (#3191)

Taskfile.yml

@@ -184,6 +184,10 @@ tasks:
     cmds:
       - cargo build --all-targets --all-features
       - cargo build --all-targets --all-features --target=wasm32-unknown-unknown
+      # Build without features, as the dependencies have slightly different
+      # features themselves and so require recompiling. This is only useful for
+      # caching.
+      - cargo build --all-targets
       - task: build-web
 
   test-all:
@@ -194,8 +198,11 @@ tasks:
       Running this isn't required when developing; it's for caching or as a reference.
 
     cmds:
-      # TODO: this doesn't run the python tests. We should add them in here.
-      # They are run in `test-all.yaml` on GHA.
+      # TODO:
+      # - Add `prql-python` tests.
+      # - We could add `prql-lib` here.
+      # - We deliberately don't test some other bindings, such as `prql-php`,
+      #   given they require more dependencies and aren't yet supported.
       - task: test-rust
       - task: build-all
       - task: test-js