build(deps): move cspell and typedoc to devDependencies

[masaru87]

cspell and typedoc are listed under dependencies, but they are only used by the spellcheck and build:docs scripts. Nothing under src/ imports either of them, and the published package only ships dist/.

Because they are runtime dependencies, every application that installs @moneytree/mt-link-javascript-sdk installs them too. Measured with npm against the published 5.1.0:

	packages	node_modules	npm audit
current	228	72 MB	9 high
without cspell/typedoc	62	4.3 MB	0

All nine advisories come from the cspell/typedoc trees (brace-expansion, minimatch, glob, rimraf, flat-cache, file-entry-cache), so they show up in consumers' audits even though neither tool ever runs in their app.

Verified locally with this change applied:

• yarn install — yarn.lock is unchanged (Yarn 4 records workspace dependencies in a single list, so moving between sections does not affect it)
• yarn test — 15 suites / 110 tests pass
• yarn lint — same 4 pre-existing warnings, no new ones
• yarn build — succeeds; the regenerated dist/ is byte-identical
• yarn build:docs and yarn spellcheck — still work, since both tools remain installed for development

This will conflict trivially with #225 (typedoc bump) depending on which lands first — happy to rebase.

[mt-ytaher]

same as #237