Testing: add GitHub action to check all lines are <= 80 characters

[cconlon]

This PR adds a GitHub action that checks to make sure all added lines are <= 80 characters, to match internal coding standards.

• Only checks ./src, ./examples, and ./jni directories
• Prints out all occurrences of long lines found to actions log

Example of a failure run: https://github.com/wolfSSL/wolfcrypt-jni/actions/runs/16231643997/job/45835457598?pr=126

[Copilot]

Pull Request Overview

Adds a GitHub Actions workflow that enforces an 80-character maximum on newly added lines in src/, examples/, and jni/ directories.

• Introduces .github/workflows/line-length-check.yml to run on all pull requests
• Scans only changed files under the target directories and fails if any added line exceeds 80 characters

Comments suppressed due to low confidence (3)

.github/workflows/line-length-check.yml:33

• [nitpick] Consider using mktemp to generate unique temporary filenames instead of fixed names (violations.tmp and changed_files.txt) to avoid collisions and streamline cleanup.

        echo > violations.tmp

.github/workflows/line-length-check.yml:41

• [nitpick] You can simplify the two-step grep filter by matching only added lines that don't start with multiple pluses: e.g., grep -E '^+[^+]' to avoid the separate grep -v '^+++'.

            git diff "origin/$BASE_BRANCH"...HEAD "$file" | \

.github/workflows/line-length-check.yml:49

• Include the offending line number in the output (e.g., using grep -n) so developers can directly locate and fix the long line without running additional commands.

                  echo "❌ $file - Line too long ($char_count characters)"