Merge `develop` into `main` for v0.6.0 Release

Description

This pull request merges the develop branch into the main branch in preparation for the v0.6.0 release. This release includes a comprehensive set of new features, bug fixes, and documentation updates that have been added since v0.5.2. The updates are thoroughly tested and documented, ensuring a smooth transition to the main branch.

Changes:

New Features:
- SanitizerFunc for input sanitization.
- GitHub Actions workflow optimizations.
- Max size limit for attachments.
- Encapsulation of EmailMessage and Attachment structs.
- Separation of email providers into individual packages.
Enhancements:
- Simplified type aliasing in the gomail package.
- Moved common components to a dedicated directory.
Bug Fixes:
- Corrected attachment encoding for Microsoft365.
- Fixed minor documentation issues.
- Replaced deprecated ioutil.ReadFile with os.ReadFile.
- Fixed CI: pin FOSSA Action to a specific commit hash.
Documentation Updates:
- Updated README.
- Comprehensive update to the changelog reflecting all changes.
- Updated package documentation.
- Updated security supported versions.
Testing:
- Extended email tests for providers.
Continuous Integration Updates:
- Updated Github actions to use a specific commit for versioning.
Dependencies:
- Updated Go version to 1.22.5.
- Bumped Go module dependencies.

Checklist

Please ensure the following guidelines are met:

[x] The code follows the style guidelines of this project.
[x] A self-review has been performed on the code.
[x] The code is well-documented, and comments have been added where necessary.
[x] Tests have been added to prove that the fix is effective or that the feature works. All existing tests pass.
[x] Commit messages follow the convention type(scope): description.
[x] The pull request has no conflicts with the base branch.
[x] Any dependent changes have been merged and published in downstream modules.

Additional Information

This pull request incorporates all changes listed in the changelog and on the releases page, ensuring a comprehensive and well-documented update for v0.6.0.

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

@@           Coverage Diff           @@
##             main      #58   +/-   ##
=======================================
  Coverage        ?   92.67%           
=======================================
  Files           ?       19           
  Lines           ?      846           
  Branches        ?        0           
=======================================
  Hits            ?      784           
  Misses          ?       34           
  Partials        ?       28

Flag	Coverage Δ
unittests	`92.67% <100.00%> (?)`

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
common/attachment.go	`100.00% <100.00%> (ø)`
common/email.go	`100.00% <100.00%> (ø)`
common/utils.go	`100.00% <100.00%> (ø)`
common/validation.go	`100.00% <100.00%> (ø)`
credentials/helpers.go	`100.00% <ø> (ø)`
gomail.go	`100.00% <100.00%> (ø)`
providers/gmail/gmail_email_sender.go	`71.42% <100.00%> (ø)`
providers/mailgun/mailgun_email_sender.go	`100.00% <100.00%> (ø)`
providers/mandrill/mandrill_email_sender.go	`96.29% <100.00%> (ø)`
...roviders/microsoft365/microsoft365_email_sender.go	`78.72% <100.00%> (ø)`
... and 9 more

darkrockmountain / gomail