docs: clarify npm version behavior with prerelease versions (#8735)

## Summary

This PR clarifies the documentation for `npm version` to explicitly
describe its behavior when the current version is a prerelease version.

## Problem

The current documentation states that when using `patch`, `minor`, or
`major` arguments, "the existing version will be incremented by 1 in the
specified field." However, this is incomplete and misleading when the
current version is a prerelease.

When the current version is a prerelease (e.g., `1.2.0-5`), running `npm
version patch` (or `minor`/`major`) will simply remove the prerelease
suffix without incrementing the version number. The result would be
`1.2.0`, not `1.2.1`.

This undocumented behavior has led to:
- Developer confusion when the version doesn't increment as expected
- Incorrect guidance from LLMs trained on the incomplete documentation

## Solution

Added a note immediately after the existing sentence to clarify this
behavior:

> **Note:** If the current version is a prerelease version, `patch`,
`minor`, and `major` will simply remove the prerelease suffix without
incrementing the version number. For example, `1.2.0-5` becomes `1.2.0`
with `npm version patch`, not `1.2.1`.

## Testing

The documentation change is straightforward and doesn't affect code
behavior. The example provided matches the actual behavior of the
`semver.inc` function from the node-semver package.

Fixes #8637

Author: yashwantbezawada

docs/lib/content/commands/npm-version.md

@@ -21,6 +21,8 @@ The `newversion` argument should be a valid semver string, a valid second argume
 In the second case, the existing version will be incremented by 1 in the specified field.
 `from-git` will try to read the latest git tag, and use that as the new npm version.
 
+**Note:** If the current version is a prerelease version, `patch` will simply remove the prerelease suffix without incrementing the patch version number. For example, `1.2.0-5` becomes `1.2.0` with `npm version patch`, not `1.2.1`.
+
 If run in a git repo, it will also create a version commit and tag.
 This behavior is controlled by `git-tag-version` (see below), and can be disabled on the command line by running `npm --no-git-tag-version version`.
 It will fail if the working directory is not clean, unless the `-f` or `--force` flag is set.