Added manage external storage permission

[JDDV]

✨ What kind of change does this PR introduce? (Bug fix, feature, docs update...)

Introduces the 'Manage External Storage' permission

⤵️ What is the current behavior?

🆕 What is the new behavior (if this is a feature change)?

💥 Does this PR introduce a breaking change?

No

🐛 Recommendations for testing

📝 Links to relevant issues/docs

🤔 Checklist before submitting

• I made sure all projects build.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy.
• I updated CHANGELOG.md to add a description of the change.
• I followed the style guide lines (code style guide).
• I updated the relevant documentation.
• I rebased onto current master.

[codecov]

Codecov Report

Merging #524 (12e6ded) into master (a1c2f07) will decrease coverage by 12.08%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##            master     #524       +/-   ##
============================================
- Coverage   100.00%   87.91%   -12.09%     
============================================
  Files            1        6        +5     
  Lines           16       91       +75     
============================================
+ Hits            16       80       +64     
- Misses           0       11       +11     

Impacted Files	Coverage Δ
...andler_platform_interface/lib/src/permissions.dart	100.00% <ø> (ø)
permission_handler/lib/permission_handler.dart
..._platform_interface/lib/src/permission_status.dart	68.18% <0.00%> (ø)
..._interface/lib/src/method_channel/utils/codec.dart	100.00% <0.00%> (ø)
...hod_channel/method_channel_permission_handler.dart	100.00% <0.00%> (ø)
...ler_platform_interface/lib/src/service_status.dart	73.33% <0.00%> (ø)
...lib/src/permission_handler_platform_interface.dart	100.00% <0.00%> (ø)

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[mvanbeusekom]

Looks good to me, just wanted to bump the version as a feature (so to 3.2.0).

[mvanbeusekom]

I think we can update this as a new feature release:

Suggested change

	version: 3.1.4
	version: 3.2.0

[mvanbeusekom]

I think we should introduce this as a new feature release:

Suggested change

	## 3.1.4
	## 3.2.0