docs: Consistent contributing.md for all roles - allow role specific contributing.md section

[richm]

Provide a single, consistent contributing.md for all roles. This mostly links to and summarizes https://linux-system-roles.github.io/contribute.html

Allow for a role specific section which typically has information about role particulars, role debugging tips, etc.

See https://github.com/linux-system-roles/.github/pull/19

Signed-off-by: Rich Megginson rmeggins@redhat.com

[codecov[bot]]

Codecov Report

Patch and project coverage have no change.

Comparison is base (2d972ee) 13.90% compared to head (905a98b) 13.90%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #350 +/- ## ======================================= Coverage 13.90% 13.90% ======================================= Files 8 8 Lines 1705 1705 Branches 71 71 ======================================= Hits 237 237 Misses 1468 1468 ``` | Flag | Coverage Δ | | |---|---|---| | sanity | `16.54% <ø> (ø)` | | 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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