feat(recommended)!: add four rules to recommended

[JasonWeinzierl]

BREAKING CHANGE: RxJS ^7.2.0 is required.

BREAKING CHANGE: recommended configuration had 4 rules added to it. See full changelog for details.

Resolves #35 .

• no-topromise: toPromise() was deprecated by RxJS, so this will be very useful for helping developers migrate to one of the two manual editor suggestions (lastValueFrom or firstValueFrom).
• prefer-observer: RxJS deprecated non-observer object subscribes, so this will help migrate.
• prefer-root-operators: RxJS moved operators to root in 7.2.0 and deprecated the old site, so this will help migrate.
  • This change requires bumping the RxJS peer dependency to 7.2.0 because 7.0.0 doesn't export the operators from root.
• throw-error: This rule will rarely be triggered because it was recently changed to only apply to the static creation function throwError(). But in those rare cases, it should always be enforced, similar to no-implicit-any-catch.

[github-actions]

LCOV of commit f5010e8 during .github/workflows/ci.yml #157

Summary coverage rate:
  lines......: 96.3% (3693 of 3835 lines)
  functions..: 95.6% (238 of 249 functions)
  branches...: 91.3% (732 of 802 branches)

Files changed coverage rate:
                                         |Lines       |Functions  |Branches    
  Filename                               |Rate     Num|Rate    Num|Rate     Num
  =============================================================================
  src/configs/recommended.ts             | 100%     28| 100%     1| 100%      1
  src/rules/no-topromise.ts              |94.9%     98| 100%     4|82.6%     23
  src/rules/prefer-observer.ts           | 100%    126| 100%     6|97.2%     36
  src/rules/prefer-root-operators.ts     |94.9%    138| 100%    16|90.7%     43
  src/rules/throw-error.ts               | 100%     77| 100%     5|93.3%     15