feat!: get completions camel case

[McPatate]

• make API camelCase for consistency
• sync docs with incremental changes
• make sure indexes are not out of bounds and avoid panicking using safe methods to get value from ropes

Should fix huggingface/llm-vscode#107

[github-actions]

Repository name	Source type	Average hole completion time (s)	Pass percentage
lancedb/lance	github	90.3676	69.465034%
helix-editor/helix	github	77.732796	70%
huggingface/huggingface_hub	github	18.878199	100%
encode/starlette	github	36.6834	89.73298%
tkaitchuck/constrandom	github	2.958	30.000002%
mmaitre314/picklescan	github	4.363	100%
tiangolo/fastapi	github	88.2744	79.91882%
colinhacks/zod	github	53.7531	80%
smol-rs/async-executor	github	8.4392	50%
lancedb/lancedb	github	70.88979	80%
jaemk/cached	github	33.6503	100%
simple	local	2.81704	93%
gcanti/io-ts	github	61.9263	100%
Total	--	26.18575	85.414406%

Note: The "hole completion time" represents the full process of:

• replacing the code from the file with a completion from the model
• building the project
• running the tests