Prepare release v5.19.0

[adidahiya]

Fixes #4812

v5.19.0

• [bugfix] relax promise-function-async for short parenthesized arrow functions (Allowed parenthesis bodies for one-line promise-function-async functions #4765)
• [bugfix] fix no-async-without-await false positive for abstract methods (no-async-without-await: check type property and add tests #4782)
• [bugfix] fix strict-comparison false positive for null and undefined literals (Fix strict comparison false positive #4786)
• [bugfix] improve no-angle-bracket-type-assertion autofix semantics with more parentheses (no-angle-bracket-type-assertion: check only for binary expression #4823)
• [enhancement] add BigInt support to restrict-plus-operands rule (fix: add bigint support to restrict-plus-operand rule #4814)
• [enhancement] await-promise now supports new TypeScript 3.6 AST API symbols for async iterators (Allowed new 'AsyncGenerator' name for await-promise async iterables #4800)
• [new-rule-option] check-strings and check-regex options for max-line-length rule ([max-line-length] ignore strings and regex in max line length #4798)
• [new-rule-option] variable-declaration-ignore-function option for typedef rule ([new-rule-option] Introduce new typedef rule option (variable-declaration-ignore-function) #4769)
• [new-rule-option] ignore-blank-lines option for object-literal-sort-keys rule (fix: add option to enforce alphabetical ordering regardless of blank lines #4808)
• [new-rule] no-for-in (Add noForIn rule #4747)
• [new-rule] no-invalid-void ([new-rule] Added new invalid-void rule #4736)
• [new-rule] strict-string-expressions reports errors on type coercions found in string expressions (Add rule: strict-string-expressions #4807)
• [new-rule] 'no-promise-as-boolean' (Add rule 'no-promise-as-boolean' #4790)
• [docs] link to OSS fellowship medium post in README (Link to OSS fellowship medium post in README #4821)