docs: auto-generate rule docs

[JasonWeinzierl]

• Add eslint-doc-generator and run on existing documentation.
  • Update existing rule descriptions to align across both rule description and markdown header.
  • Add Configs section to README.
• Add markdownlint.

[github-actions]

LCOV of commit 4e8e0a7 during .github/workflows/ci.yml #22

Summary coverage rate:
  lines......: 96.2% (3249 of 3376 lines)
  functions..: 92.9% (196 of 211 functions)
  branches...: 91.2% (613 of 672 branches)

Files changed coverage rate:
                                         |Lines       |Functions  |Branches    
  Filename                               |Rate     Num|Rate    Num|Rate     Num
  =============================================================================
  src/rules/ban-observables.ts           | 100%     64| 100%     3|93.3%     15
  src/rules/ban-operators.ts             | 100%     63| 100%     2|93.3%     15
  src/rules/finnish.ts                   |96.0%    276| 100%    20|92.9%     85
  src/rules/just.ts                      | 100%     43| 100%     3| 100%      8
  src/rules/macro.ts                     | 100%     63| 100%     5| 100%     10
  src/rules/no-async-subscribe.ts        | 100%     46| 100%     2| 100%      3
  src/rules/no-compat.ts                 | 100%     27| 100%     1| 100%      2
  src/rules/no-connectable.ts            | 100%     38| 100%     3| 100%      6
  src/rules/no-create.ts                 | 100%     32| 100%     2| 100%      2
  src/rules/no-cyclic-action.ts          |88.9%    108| 100%     4|68.4%     19
  src/rules/no-explicit-generics.ts      | 100%     53| 100%     4| 100%     10
  src/rules/no-exposed-subjects.ts       |96.5%    113| 100%     2|86.7%     15
  src/rules/no-finnish.ts                |99.0%    103| 100%    16|87.5%     24
  src/rules/no-ignored-error.ts          | 100%     37| 100%     2| 100%      5
  src/rules/no-ignored-notifier.ts       | 100%     76| 100%     5| 100%     14
  src/rules/no-ignored-observable.ts     | 100%     29| 100%     2| 100%      3
  src/rules/no-ignored-replay-buffer.ts  | 100%     51| 100%     5| 100%      6
  src/rules/no-ignored-subscribe.ts      | 100%     35| 100%     2| 100%      4
  src/rules/no-ignored-subscription.ts   | 100%     37| 100%     2| 100%      6
  src/rules/no-ignored-takewhile-value.ts| 100%     56| 100%     4| 100%     14
  src/rules/no-implicit-any-catch.ts     |98.7%    157| 100%     6|96.6%     29
  src/rules/no-index.ts                  | 100%     27| 100%     1| 100%      2
  src/rules/no-internal.ts               |86.8%     76| 100%     3|78.9%     19
  src/rules/no-nested-subscribe.ts       | 100%     49| 100%     1| 100%     11
  src/rules/no-redundant-notify.ts       |84.4%     90| 100%     4|53.3%     15
  src/rules/no-sharereplay.ts            | 100%     49| 100%     2| 100%      7
  src/rules/no-subclass.ts               | 100%     44| 100%     1| 100%      4
  src/rules/no-subject-unsubscribe.ts    | 100%     47| 100%     3| 100%      4
  src/rules/no-subject-value.ts          |94.3%     35| 100%     2|66.7%      3
  src/rules/no-subscribe-handlers.ts     | 100%     34| 100%     2| 100%      4
  src/rules/no-tap.ts                    | 100%     35| 100%     1| 100%      2
  src/rules/no-topromise.ts              | 100%     31| 100%     1| 100%      3
  src/rules/no-unbound-methods.ts        |97.2%     72| 100%     6|92.9%     14
  src/rules/no-unsafe-catch.ts           |95.5%     66| 100%     3|77.8%      9
  src/rules/no-unsafe-first.ts           |97.2%     72| 100%     2|90.0%     10
  src/rules/no-unsafe-subject-next.ts    | 100%     53| 100%     1| 100%     14
  src/rules/no-unsafe-switchmap.ts       |96.9%    128| 100%     3|89.3%     28
  src/rules/no-unsafe-takeuntil.ts       |96.3%    109| 100%     2|88.9%     18
  src/rules/prefer-observer.ts           | 100%    125| 100%     6|97.2%     36
  src/rules/suffix-subjects.ts           |90.8%    206|94.1%    17|82.0%     50
  src/rules/throw-error.ts               | 100%     51| 100%     3| 100%      7