Feat/text file attach

[satoxiw]

Issue #, if available:

Description of changes: テキストファイルをリクエストに添付できる機能を追加しました。 MIME Typeで"text/*"となるものが対象ですが、環境によってはMIME Typeが正しく設定されないケースがあり、その場合は拡張子で判断するようになっています。対象となる拡張子は下記コード中に埋めていますが、これだと対象を追加しにくいかもしれないので、何か良い案があったらご指摘ください。 https://github.com/aws-samples/bedrock-claude-chat/compare/v1...satoxiw:bedrock-claude-chat:feat/text-file-attach?expand=1#diff-4f4332c2118277ddc90f75e9489ace8c6be3e9c60c88165e58063e8f25aa4734R37

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[Yukinobu-Mine]

拡張子からの MIME type の推定は、このあたりのライブラリが使えそうです。 (既にフロントエンドの依存関係に含まれてるので、import するだけで使えると思います) https://www.npmjs.com/package/mime

このライブラリが内部的に参照してるマッピング情報はこちらのようです。 https://github.com/jshttp/mime-db/blob/master/db.json

[statefb]

Related issue: #198 Partially solved

[statefb]

getAllTextExtensionsした結果をそのままhard codingしてしまった方が早い？

["appcache","manifest","ics","ifb","coffee","litcoffee","css","csv","html","htm","shtml","jade","js","mjs","jsx","less","md","markdown","mml","mdx","n3","txt","text","conf","def","list","log","in","ini","dsc","rtx","rtf","sgml","sgm","shex","slim","slm","spdx","stylus","styl","tsv","t","tr","roff","man","me","ms","ttl","uri","uris","urls","vcard","curl","dcurl","mcurl","scurl","sub","ged","fly","flx","gv","3dml","spot","jad","wml","wmls","vtt","wgsl","s","asm","c","cc","cxx","cpp","h","hh","dic","htc","f","for","f77","f90","hbs","java","lua","mkd","nfo","opml","org","p","pas","pde","sass","scss","etx","sfv","ymp","uu","vcs","vcf","xml","yaml","yml"]