Streamly documentation/guide fixes

[harendra-kumar]

Types and modules:

• Streamly.Data.Scan changed to Scanl
• RingArray is exposed
• Path module names changed
• FileSyste.Event modules moved

replacing-other-packages:

• splitOn has changed
• Scanl instead of Scan
• RingArray is not internal
• FileSystem.Event has moved
• Path module names have changed

performance-considerations:

• RingArray is exposed

module structure and quick examples:

• Scan changed to Scanl

Api changelogs:

split the 0.8.3 api changelog into parts

Reorder the "project" TOC.

• changelog/upgrading should be together
• credits/contributors should be together
• README should be the first, then changelogs then credits

Add other packages:

• streamly-text
• streamly-filepath

streamly-fsevents does not show a readme in docs.

[adithyaov]

See: https://github.com/composewell/streamly/compare/misc-doc-fixes?expand=1

Unclear on:

Types and modules:

• [x] RingArray is exposed
• [x] Path module names changed

replacing-other-packages:

• [x] RingArray is not internal

performance-considerations:

• [x] RingArray is exposed

Api changelogs:

split the 0.8.3 api changelog into parts

Reorder the "project" TOC.

• [ ] changelog/upgrading should be together
• [ ] credits/contributors should be together
• [ ] README should be the first, then changelogs then credits

Add other packages:

• [ ] streamly-text

• [ ] streamly-filepath

• [ ] streamly-fsevents does not show a readme in docs.

[harendra-kumar]

Fix link to streamly-packages in before-you-begin doc.

[harendra-kumar]

Change order of the project directory items as rendered on the website: