doc: add startLTS usage examples

[ruyadorno]

I reach to node-core-utils for automating the LTS release commit but I couldn't get it to work due to the lack of a proper usage example.

I'm adding examples to both the markdown docs and the cli help output which are the places I would have loved to have found these.

CLI help output

Before

$ git node release --help
git-node release [newVersion|options]

Manage an in-progress release or start a new one.

Positionals:
  newVersion, options  Version number of the release to be prepared or promoted

Options:
  --version   Show version number                                      [boolean]
  --help      Show help                                                [boolean]
  --prepare   Prepare a new release of Node.js                         [boolean]
  --promote   Promote new release of Node.js                           [boolean]
  --security  Demarcate the new security release as a security release [boolean]
  --startLTS  Mark the release as the transition from Current to LTS   [boolean]

Examples:
  git node release --prepare 1.2.3  Prepare a new release of Node.js tagged v1.2
                                    .3

After

$ git node release --help
git-node release [newVersion|options]

Manage an in-progress release or start a new one.

Positionals:
  newVersion, options  Version number of the release to be prepared or promoted

Options:
  --version   Show version number                                      [boolean]
  --help      Show help                                                [boolean]
  --prepare   Prepare a new release of Node.js                         [boolean]
  --promote   Promote new release of Node.js                           [boolean]
  --security  Demarcate the new security release as a security release [boolean]
  --startLTS  Mark the release as the transition from Current to LTS   [boolean]

Examples:
  git node release --prepare 1.2.3  Prepare a release of Node.js tagged v1.2.3
  git node --prepare --startLTS     Prepare the first LTS release

Signed-off-by: Ruy Adorno ruyadorno@google.com

cc @BethGriggs @richardlau @RafaelGSS

[codecov]

Codecov Report

Base: 84.03% // Head: 83.60% // Decreases project coverage by -0.42% ⚠️

Coverage data is based on head (bf72e4c) compared to base (4e59a64).
Patch has no changes to coverable lines.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #654      +/-   ##
==========================================
- Coverage   84.03%   83.60%   -0.43%     
==========================================
  Files          37       37              
  Lines        4077     4117      +40     
==========================================
+ Hits         3426     3442      +16     
- Misses        651      675      +24     

Impacted Files	Coverage Δ
lib/ci/run_ci.js	78.33% <0.00%> (-21.67%)	⬇️
lib/verbosity.js	80.76% <0.00%> (+7.69%)	⬆️

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