Add `.swift-format` to the repo and format the repo with `swift-format`.
This commit does not add any automation to enforce formatting of sourcekit-lsp in CI. The goal of this commit is to get the majority of source changes out of the way so that the diff of actually enforcing formatting will have fewer changes or conflicts.
#481 replaced SourceKit placeholders (like `<#code#>`) by LSP snippets for code actions, which are used to represent SourceKit refactoring and diagnostic Fix-Its. But LSP snippets are only supported for code completion, not for code actions. This results in LSP snippets like ${1:code} being inserted into the editor.
Instead of replacing SourceKit placeholders by LSP placeholders, we should just remove them altogether from the code action response.
rdar://92447079 [#488]
We will be able to split the LSP modules off later. These LSP modules
will provide the ability to write custom LSP servers and clients in
Swift. The sourcekit-lsp repository will build on top of this new
package to provide an LSP implementation that creates a language server
for Swift and C-based-languages.
