Allow alphanumeric characters in SQLLite style parameters.

[BlurrechDev]

• I've made "$" a valid identifier in get_ident_named_placeholder_token().
• Added some tests mixing indexed and named parameters.
• Adjusting the parameter precedence based on the initial QueryParams provided. (Named vs Indexed).
• The first commit 766c923 was sufficient to get to where I wanted to get, the rest just addresses mixed parameter types which might not actually be a real issue anyway...

Attempts to fix #18

I don't have a Rust background so there may be better ways of doing this.

Happy to adjust as necessary or throw out the lot as it may be.

Thanks.

[shssoichiro]

The code looks good. Would you be able to run cargo fmt and push up the changes?

[BlurrechDev]

@shssoichiro Sorted. I had to rejig the token ordering so this would play nicely with the very recent $$ change.

[max-sixty]

Thanks for these @BlurrechDev

@shssoichiro if you'd be up for doing a release, I'd love to integrate this into PRQL

[shssoichiro]

Published, thanks!