Documentation for assets module (#1945)

* WIP - SRML Assets Module README

* docs: Tweaks for consistency

* docs: Add missing newline

* review-fix: Remove non-SRML trait dependencies

* review-fix: Replace const with let

* review-fix: Remove use of compact in signature

* review-fix: Change const to let since cannot use result of function call

* fix: Add backticks around type and mention type it derives from

* review-fix: Update variable names since changed to lowercase since using let

* fix: Change type to bold instead of code

* review-fix: Update Asset module

* refactor: Consistent bullet points. Remove whitespace between items

* review-fix: Remove useless blah

* review-fix: Remove Storage Items

* review-fix: Remove Types

* review-fix: Remove duplicate instructions

* Update srml/assets/src/lib.rs

Co-Authored-By: ltfschoen <[email protected]>

* Update srml/assets/src/lib.rs

Co-Authored-By: ltfschoen <[email protected]>

* Update srml/assets/src/lib.rs

Co-Authored-By: ltfschoen <[email protected]>

* Update srml/assets/src/lib.rs

Co-Authored-By: ltfschoen <[email protected]>

* Update srml/assets/src/lib.rs

Co-Authored-By: ltfschoen <[email protected]>

* Update srml/assets/src/lib.rs

Co-Authored-By: ltfschoen <[email protected]>

* Update srml/assets/src/lib.rs

Co-Authored-By: ltfschoen <[email protected]>

* Update srml/assets/src/lib.rs

Co-Authored-By: ltfschoen <[email protected]>

* Update srml/assets/src/lib.rs

Co-Authored-By: ltfschoen <[email protected]>

* Update srml/assets/src/lib.rs

Co-Authored-By: ltfschoen <[email protected]>

* Update srml/assets/src/lib.rs

Co-Authored-By: ltfschoen <[email protected]>

* Update srml/assets/src/lib.rs

Co-Authored-By: ltfschoen <[email protected]>

* Update srml/assets/src/lib.rs

Co-Authored-By: ltfschoen <[email protected]>

* Update srml/assets/src/lib.rs

Co-Authored-By: ltfschoen <[email protected]>

* Update srml/assets/src/lib.rs

Co-Authored-By: ltfschoen <[email protected]>

* review-fix: Remove since will be replaced after macro expansion #2068 as per comment

* review-fix: Move Goals within overview

* fix: Fix indentation

* style and a few minor changes

* remove Events

* capitalization

* docs: Reword the Goals to remove mention of cold wallets based on discussion with Joe

* Wording

* Update lib.rs

* Update lib.rs

* Update lib.rs