message: Update changelog for 2.10.0 release
diff: ## Upcoming
  - `apollo`
  - - Add `client:download-schema` command to download schemas from engine to an output file [#1108](https://github.com/apollographql/apol lo-tooling/pull/1108)
  + - <First `apollo` related entry goes here>
  - `apollo-codegen-core`
  - <First `apollo-codegen-core` related entry goes here>
  - `apollo-codegen-flow`
  - `vscode-apollo`
  - <First `vscode-apollo` related entry goes here>
  +## `apollo@2.10.0`
  +
  +- `apollo@2.10.0`
  + - Add `client:download-schema` command to download schemas from engine to an output file [#1108](https://github.com/apollographql/apollo-tooling/pull/1108)
  +
  ## `apollo@2.9.0`, `apollo-language-server@1.7.0`
  - `apollo@2.9.0`
  