feat(commons): add fromBase64 helper function

[dreamorosi]

Description of your changes

This PR introduces a new helper function in the common package dedicated to decoding a base64 encoded string to a byte array.

I am adding the utility here because it will be used by both the upcoming JMESPath utility as well as the existing Parameters one.

The helper function is exposed via subpath and dedicated export, so in most cases it will be tree shaken at bundle time when not used.

import { fromBase64 } from '@aws-lambda-powertools/commons/utils/base64';

const encodedValue = 'aGVsbG8gd29ybGQ=';

const decoded = fromBase64(encodedValue);
// new Uint8Array([ 97, 71, 86, 115, 98, 71, 56, 103, 100, 50, 57, 121, 98, 71, 81, 61 ]);

Related issues, RFCs

Issue number: #2188

Checklist

• My changes meet the tenets criteria
• I have performed a self-review of my own code
• I have commented my code where necessary, particularly in areas that should be flagged with a TODO, or hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my change is effective and works
• The PR title follows the conventional commit semantics

Breaking change checklist

Is it a breaking change?: NO

• I have documented the migration process
• I have added, implemented necessary warnings (if it can live side by side)

---

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

Disclaimer: We value your time and bandwidth. As such, any pull requests created on non-triaged issues might not be successful.

[am29d]

Thanks for the PR, I have only a minor question about the export path.

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud