bashd: äldre versioner att ladda ner

## What's Changed
### Fixes:
`textDocument/documentColor`：Return empty slice instead of nil

**Full Changelog**：https://github.com/matkrin/bashd/compare/v0.3.0...v0.3.1

## What's Changed

• Configurable workspace diagnostics by @matkrin in https://github.com/matkrin/bashd/pull/10
• This adds the functionality to suppress workspace diagnostics when the
configuration updates (`workspace/didChangeConfiguration`) by the boolean
settings `workspace_diagnostics_on_update` with the default value of `true`.

• Further, there is a boolean flag `--no-workspace-diagnostics-on-update`,
serving the same purpose.

• The workspace diagnostics checking was removed from `initialize` as it was
redundant, as on startup, the initial configuration is also transferred via
`workspace/didChangeConfiguration`, i.e. diagnostics where checked twice in the
past.

### Fixes
• Omit empty `documentSymbol.children`
• Double checking of workspace diagnostics on startup

**Full Changelog**：https://github.com/matkrin/bashd/compare/v0.2.3...v0.3.0

## What's changed

• fix：Dereference of nil pointer of `clientInfo` in `initialize`

**Full Changelog**：https://github.com/matkrin/bashd/compare/v0.2.2...v0.2.3

What's changed
- fix: Omit empty optional fields of completionItem in textdocument/completion

## What's Changed

- Add snippets support by @matkrin in #1