chore: create and apply rustfmt.toml

[luisschwab]

Description

Closes #3.

This PR adds basic formatting configuration for uniform comments. Note that the nightly toolchain is necessary.

Changes:

• Add rustfmt.toml with this config:

comment_width = 140
format_code_in_doc_comments = true
wrap_comments = true

• Apply rustfmt.toml.
• Update the fmt CI job to use the nightly toolchain.
• Update PR template to use nightly toolchain.

Note: I had to add #[rustfmt::skip] to test_extract_satisfaction_timelock() because the base64 PSBT would get wrapped due to the slashes.

Checklists

All Submissions:

• I've signed all my commits
• I followed the contribution guidelines
• I ran cargo +nightly fmt and cargo clippy before committing

Bugfixes:

• This pull request breaks the existing API
• I've added tests to reproduce the issue which are now passing
• I'm linking the issue being fixed by this PR

[coveralls]

Pull Request Test Coverage Report for Build 14543825347

Details

• 21 of 21 (100.0%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.01%) to 86.537%

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Totals
Change from base Build 14270666930:	0.01%
Covered Lines:	7276
Relevant Lines:	8408

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💛 - Coveralls

[notmandatory]

I didn't realize this would require +nightly. Any idea when the fmt features we need will be in a stable release?

[notmandatory]

ACK 0b5e3f6

It's a little ackward to have to use cargo +nightly fmt but since it only needs to be done before pushing the PR and will make all the docs and docs tests more consistent I'd still like to do it.

[luisschwab]

Any idea when the fmt features we need will be in a stable release?

Not sure, but once it's in stable we can revert it.

By the way, I made an identical PR on bdk as well.