feat: adjust vertical and horizontal message spacing

[MartinCupela]

🎯 Goal

Closes REACT-788

1. Apply horizontal spacing and alignment between message composer and message lists

2. Add avatar display control using new showAvatar ('incoming', 'outgoing', boolean) prop in MessageProps - necessary to make it easier for the integrators to apply specific styles that would remove grid column reserved for avatars. Default is 'incoming'

3. Apply vertical spacing between message groups and within message groups applying the following rules:

• keep gap of 4px between messages in a group
• keep gap 16px between message groups

🎨 UI Changes

Wide screen

Narrow screen

[github-actions]

Size Change: +4.05 kB (+1.04%)

Total Size: 393 kB

Filename	Size	Change
./dist/Channel-BAWilRxu.js	0 B	-20.7 kB (removed)	🏆
./dist/Channel-EXpv8hMv.js	20.8 kB	+20.8 kB (new file)	🆕
./dist/cjs/emojis.js	2.98 kB	+1 B (+0.03%)
./dist/cjs/index.js	196 kB	+2.75 kB (+1.42%)
./dist/css/emojis.css	0 B	-113 B (removed)	🏆
./dist/css/index.css	33.9 kB	+1.34 kB (+4.13%)

ℹ️ View Unchanged

Filename	Size
./dist/audioProcessing-BbOs2wMd.js	1.32 kB
./dist/ChannelPreview-DZQGasqq.js	6.84 kB
./dist/cjs/experimental.js	3.62 kB
./dist/cjs/mp3-encoder.js	1.27 kB
./dist/css/v2/emoji-mart.css	1.84 kB
./dist/css/v2/emoji-replacement.css	300 B
./dist/css/v2/index.css	39.4 kB
./dist/css/v2/index.layout.css	22.8 kB
./dist/limits-BeZVeL84.js	61.8 kB

_{compressed-size-action}