docs: Update flame_audio readme

[xjyribro]

Description

Closes: #2511

Checklist

• I have followed the Contributor Guide when preparing my PR.
• I have updated/added tests for ALL new/updated/fixed functionality.
• I have updated/added relevant documentation in docs and added dartdoc comments with ///.
• I have updated/added relevant examples in examples or docs.

Breaking Change?

• Yes, this PR is a breaking change.
• No, this PR is not a breaking change.

Related Issues

[xjyribro]

@spydon

For issue #2511

[spydon]

Nice! It would be good to have an example of how to use AudioPool too, and there are some issues that the markdown linter complains on that should be fixed:

 packages/flame_audio/README.md:32 MD022/blanks-around-headings Headings should be surrounded by blank lines [Expected: 2; Actual: 1; Above] [Context: "## How to use"]
packages/flame_audio/README.md:41 MD022/blanks-around-headings Headings should be surrounded by blank lines [Expected: 2; Actual: 1; Above] [Context: "### General sounds"]
packages/flame_audio/README.md:61 MD022/blanks-around-headings Headings should be surrounded by blank lines [Expected: 2; Actual: 1; Above] [Context: "### Background music"]
packages/flame_audio/README.md:63:38 MD009/no-trailing-spaces Trailing spaces [Expected: 0 or 2; Actual: 1]
packages/flame_audio/README.md:64 MD031/blanks-around-fences Fenced code blocks should be surrounded by blank lines [Context: "```dart"]
packages/flame_audio/README.md:96 MD022/blanks-around-headings Headings should be surrounded by blank lines [Expected: 2; Actual: 1; Above] [Context: "### Caching"]
packages/flame_audio/README.md:98:101 MD013/line-length Line length [Expected: 100; Actual: 172]
packages/flame_audio/README.md:119 MD012/no-multiple-blanks Multiple consecutive blank lines [Expected: 2; Actual: 3]

[spydon]

What changed here?

[spydon]

Probably just revert this change, I'm guessing it is some change of the symlink?
The MD linter crashes on it now:

Error: ENOENT: no such file or directory, open 'packages/flame/README.md'
    at Object.openSync (node:fs:596:3)
    at Object.readFileSync (node:fs:464:35)
    at lintFile (/opt/hostedtoolcache/node/18.20.1/x64/lib/node_modules/markdownlint-cli/node_modules/markdownlint/lib/markdownlint.js:852:33)
    at lintWorker (/opt/hostedtoolcache/node/18.20.1/x64/lib/node_modules/markdownlint-cli/node_modules/markdownlint/lib/markdownlint.js:937:7)
    at lintInput (/opt/hostedtoolcache/node/18.20.1/x64/lib/node_modules/markdownlint-cli/node_modules/markdownlint/lib/markdownlint.js:978:7)
    at Function.markdownlintSync [as sync] (/opt/hostedtoolcache/node/18.20.1/x64/lib/node_modules/markdownlint-cli/node_modules/markdownlint/lib/markdownlint.js:1027:3)
    at lintAndPrint (/opt/hostedtoolcache/node/18.20.1/x64/lib/node_modules/markdownlint-cli/markdownlint.js:319:35)
    at Object.<anonymous> (/opt/hostedtoolcache/node/18.20.1/x64/lib/node_modules/markdownlint-cli/markdownlint.js:325:5)
    at Module._compile (node:internal/modules/cjs/loader:1364:14)
    at Module._extensions..js (node:internal/modules/cjs/loader:1422:10) {
  errno: -2,
  syscall: 'open',
  code: 'ENOENT',
  path: 'packages/flame/README.md'
}

[xjyribro]

I didn't maually edit this file. I ran melos markdown-fix. I believe it fixed this error: packages\flame\README.md:1:15 MD047/single-trailing-newline Files should end with a single newline character

[spydon]

Alright, interesting that it doesn't complain about that in the pipeline, probably some platform differences. If you just checkout the main version it will pass in the pipeline.

[spydon]

Alright, I fixed the readme file

[xjyribro]

I'm on a Windows PC so maybe some differences...

[spydon]

@xjyribro do you want to add an AudioPool example, or should be merge this as-is?

[xjyribro]

I've not used AudioPools before so I created the example based on my understanding of the docs. 06bee31

[spydon]

Lgtm