feat: add Lao (lo-LA) locale

[xubmuajkub]

Closes #2443

Adds cardinal, currency and ordinal support for Lao.

Why this is not a copy of th-TH

Lao shares script ancestry and scale vocabulary with Thai, but three things differ:

	Lao	Thai
20	ຊາວ	ຍີ່ສິບ
trailing 1 after a ten	ເອັດ — ສິບເອັດ, ຊາວເອັດ, ເກົ້າສິບເອັດ	ສິບເອັດ only
10,000	ສິບພັນ (written/finance)	ໝື່ນ

The ເອັດ forms are carried by exactWordsMapping. convertInternal consults it for chunk remainders as well as whole numbers, so 121 resolves to ໜຶ່ງຮ້ອຍຊາວເອັດ without needing an entry per hundred.

Scale

100,000 has a named scale word (ແສນ), but 10,000 does not get one: written Lao finance reads it as ສິບພັນ rather than the spoken ໝື່ນ. Leaving 10^4 unnamed lets the composer build it from ພັນ.

10000     => ສິບພັນ
20000     => ຊາວພັນ
100000    => ໜຶ່ງແສນ
792581    => ເຈັດແສນເກົ້າສິບສອງພັນຫ້າຮ້ອຍແປດສິບເອັດ
2741034   => ສອງລ້ານເຈັດແສນສີ່ສິບເອັດພັນສາມສິບສີ່

Ordinals

Lao forms ordinals with the prefix ທີ, so this uses ordinalPrefix rather than a per-number ordinalWordsMapping, matching km-KH. toOrdinal(21) → ທີຊາວເອັດ.

Currency

The kip subunit (ອັດ / att) is defunct and not used in practice, so fractional amounts are read as a decimal instead of being given a subunit name:

1234.56 => ໜຶ່ງພັນສອງຮ້ອຍສາມສິບສີ່ກີບຈຸດຫ້າສິບຫົກຖ້ວນ
500     => ຫ້າຮ້ອຍກີບຖ້ວນ

One thing I would like a maintainer's opinion on. texts.and supplies that leading ຈຸດ, because the currency converter emits texts.and before the fractional words while a fractionalUnit name would follow them. The side effect is that convert(n, { useAnd: true }) now inserts ຈຸດ between a unit word and its remainder. Lao uses no conjunction inside numbers, so useAnd is not meaningful for this locale either way — but if you would rather not overload texts.and, I am happy to drop the ຈຸດ and emit the bare digits instead, or to rework it against a small core change.

Bundle size budget

The new locale pushes the full UMD build to 70.79 KB gzip, just past the existing 70.50 KiB ceiling, so SIZE_BUDGETS.fullGzipped is raised to 71 KiB. Per-locale budgets are untouched.

Verification

All steps from CONTRIBUTING pass, plus docs:check:

npm run lint            ✓
npm run test:locale-quality  ✓
npm test -- --run       ✓  42743 tests, 100% statements/branches/functions/lines
npm run build           ✓
npm run test:runtime    ✓
npm run test:package    ✓
npm run docs:check      ✓

npm run format reports one pre-existing issue in CHANGELOG.md that is also present on a clean main; left untouched.

Also updated

• SUPPORTED_LOCALES count 135 → 136 in the manifest test, runtime smoke check, README and docs
• locale-specific numbering-system count 4 → 5
• Reviewed language identity for the lo subtag
• README locale table, docs/locales/lao.md, locales index, VitePress sidebar, NumberDemo.vue

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Additional details and impacted files

@@            Coverage Diff            @@
##              main     #2444   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          144       145    +1     
  Lines         2281      2291   +10     
  Branches       352       349    -3     
=========================================
+ Hits          2281      2291   +10     

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[mastermunj]

Thank you for your contribution @xubmuajkub. Release v7.1.0