Update crate documentation

[rajarshimaitra]

Description

After #99 the previous documentation have been removed and new docs as per structopts documentation. This PR adds more documentation across the crate..

This PR is above #102 , to accommodate all the further refactoring changes.

The Readme About section have been updated with more details.. Readme format made aligned with the BDK project itself..

The Readme file is used itself as the crate level documentation in docs.rs too..

Checklists

All Submissions:

• [x] I've signed all my commits
• [x] I followed the contribution guidelines
• [x] I ran cargo fmt and cargo clippy before committing

[rajarshimaitra]

This is rebased on top of #102 to include all the remaining code changes..

[rajarshimaitra]

Thanks for nits @waterst0ne .. Really helpful..

[rajarshimaitra]

@waterst0ne Updated with your comments..

[rajarshimaitra]

Rebased on latest #102

[rajarshimaitra]

Rebased on top of #102 ..

[rajarshimaitra]

Thanks @notmandatory for the 102 merge.. Rebased on master..

This is basic documentation update and should be straight forward to review..

[notmandatory]

@rajarshimaitra I added a commit with some small grammar and punctuation changes. For the punctuation I primarily added periods to the end of lines in the rust docs, which is how they do it in other rust docs I've seen. If these changes look OK feel free to merge the PR, or I'm happy to merge it tomorrow with your OK.

[rajarshimaitra]

Thanks @notmandatory for the review.. All looks good to me.. Merged..