fix: migrate floem to git, expand Tailwind utilities, and fix compatibility

[elcoosp]

Summary

This PR transitions the floem-tailwind dependency from a local path to the upstream floem Git repository, adapts the codebase to the latest Floem API changes, and massively expands the set of available Tailwind‑style utility methods.

Dependency Change

• From: floem = { path = "../floem" }
• To: floem = { git = "https://github.com/lapce/floem" }

This removes the local path dependency and pins to the latest Floem HEAD.

Adaptations for Upstream Floem Changes

• Replaced peniko direct dependency with floem::peniko re‑exports.
• Updated imports: PxPctAuto → LengthAuto, Weight → FontWeight, SEMIBOLD → SEMI_BOLD.
• Fixed method signatures to match current Floem API:
  • justify_content / align_items / align_self no longer take Option<…>.
  • self_auto no longer passes None to align_self, just returns self.
  • m_auto, mx_auto, … now use LengthAuto::Auto.
• Updated demo example to use the new Floem widget constructors (Stack::vertical, Label::derived, Button::new, Empty::new, etc.).

New Tailwind Utility Modules

Added traits and their scope

Module / Trait	Covers
flexbox (TailwindFlexboxExt)	Direction, wrap, grow/shrink, full basis scale (0‑96), justify/align/align‑self/align‑content
layout (TailwindLayoutExt)	Display, position, z‑index, inset‑x/y‑0, text‑overflow
interactivity (TailwindInteractivityExt)	Cursor styles, user‑select, pointer‑events
gap (TailwindGapExt)	Column‑gap and row‑gap for the full spacing scale
border_side (TailwindBorderSideExt)	Per‑side border widths (t/r/b/l, x, y)
opacity (TailwindOpacityExt)	Opacity values 5‑100 (in 5% steps)
special_colors (TailwindSpecialColorExt)	White, black, transparent (bg/text/border)
colors_ext (TailwindColorExt)	Additional 16 colour families (all shades), bringing the total to all 22 Tailwind families
leading (TailwindLeadingExt)	Line‑height utilities (numeric 3‑10, and named none‑loose)
inset (TailwindInsetExt)	Top/right/bottom/left/inset/inset‑x/inset‑y for the full 0‑96 scale
min_max_height (TailwindMinMaxHeightExt)	Min‑height and max‑height for the full 0‑96 scale
number_font_size (TailwindNumberFontSizeExt)	Numeric font‑size utilities (text_12 … text_96)

All new traits are publicly exported from lib.rs.

Colour families covered

The combination of the original TailwindExt, TailwindSpecialColorExt, and TailwindColorExt now includes:

Backgrounds, text colours, and border colours for every Tailwind family (22 families, shades 50‑950):
slate, gray, zinc, neutral, stone, red, orange, amber, yellow, lime, green, emerald, teal, cyan, sky, blue, indigo, violet, purple, fuchsia, pink, rose

Plus white, black, transparent via the special‑colours trait.

Code Quality & Testing

• Removed broken font_weight reference from old code.
• Cleaned up unnecessary mut self in new modules.
• Corrected gap utilities to use col_gap/row_gap instead of generic gap.
• Fixed and finalised inset module and integration tests.
• Added macro‑driven integration tests (tests/utilities.rs) covering every method of every new trait.
• All new code compiles and passes tests.

Documentation

• Added a comprehensive README.md for the floem-tailwind crate.
• Included a justfile with test and wr (watch) recipes.

Checklist

• Migrate floem to public Git repository
• Adapt to latest Floem API (no more Option<…>, changed types)
• Add 12 new utility traits covering the full Tailwind CSS utility set
• Extend colour palette to all 22 families
• Add integration tests for every new method
• Update demo and documentation
• Ensure all tests pass