docs: Fix multiple small issues in README.md

[vojtechtrefny]

Missing information about Stratis support, default value for grow_to_fill, notes about pool type-specific arguments etc.

Resolves: https://github.com/linux-system-roles/storage/issues/455 Resolves: https://github.com/linux-system-roles/storage/issues/428 Resolves: https://github.com/linux-system-roles/storage/issues/385 Related: https://github.com/linux-system-roles/storage/issues/437

[codecov[bot]]

Codecov Report

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

Project coverage is 10.76%. Comparing base (bb51979) to head (5e93dab). Report is 2 commits behind head on main.

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HEAD has 1 upload less than BASE

| Flag | BASE (bb51979) | HEAD (5e93dab) | |------|------|------| |sanity|1|0|

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #456 +/- ## ========================================== - Coverage 16.54% 10.76% -5.79% ========================================== Files 2 8 +6 Lines 284 1942 +1658 Branches 79 0 -79 ========================================== + Hits 47 209 +162 - Misses 237 1733 +1496 ``` | [Flag](https://app.codecov.io/gh/linux-system-roles/storage/pull/456/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=linux-system-roles) | Coverage Δ | | |---|---|---| | [sanity](https://app.codecov.io/gh/linux-system-roles/storage/pull/456/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=linux-system-roles) | `?` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=linux-system-roles#carryforward-flags-in-the-pull-request-comment) to find out more.

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[richm]

what about addressing concerns in https://github.com/linux-system-roles/storage/issues/437 and https://github.com/linux-system-roles/storage/issues/428 and https://github.com/linux-system-roles/storage/issues/385

[vojtechtrefny]

what about addressing concerns in #437 and #428 and #385

Good point, I've updated the PR to cover these issues too.