Add support for custom dictionaries

[Skadic]

This PR adds the -w/--dictionary flag, which allows specifying a dictionary file. The dictionary file contains one word on each line. These words are ignored when LanguageTool reports misspellings. Example dictionary file:

alowed
woords
go-here

If LanguageTool reports the words alowed, woords or go-here as misspellings, they are ignored and not reported.

[antonWetzel]

Thanks for the contribution.

A few things before I can merge this

• deduplicate the code to create the filter dict by moving the code into main
• make filter_response non-async
• respect UTF-8 bounds (see below)

UTF-8 Bounds

• LanguageTool (Java) uses string index at char bounds, Rust at byte bounds.
• For an example Ä Ö Ä if Ö is the typo Languagetool reports typo at offset 2 with lenght 1.
• In UTF-8 the bytes look like ÄÄ ÖÖ ÄÄ, so rust wants text[3..5].
• A way to find the UTF-8 bounds with the char_indices iterator is below.

let ctx = &m.context;
let mut chars = ctx.text.char_indices();
let start = chars.nth(ctx.offset).map_or(0, |(idx, _)| idx);
let end = chars.nth(ctx.length.wrapping_sub(1)).map_or(ctx.text.len(), |(idx, _)| idx);
let word = &ctx.text[start..end];

[Skadic]

Thanks for your answer! I changed the code accordingly.

On another note, I think I found a bug. Should I fix it here or make a new PR?

[antonWetzel]

Is merged, thanks for the help. For the bug I prefer a separate issue.