v0.7.0-beta.7

User changelog:

• fix race condition with test provider invalidating documents
• port redundant dfmt off/on checks (#74)
• add dlangui completion snippets & color provider (#77)
• add highlight provider (#82)
• DCD 0.13.5

Developer changelog:

• added Document.clone, giving an immutable document with duplicated text that can be accessed as string
• add document wordRangeAt using bytes returning bytes
• add document nextPositionBytes, which works like movePositionBytes, but using ref parameters so you don't need to reassign them on every use
• fixed some deprecations