[clang] [MC][RISCV] Add assembly syntax highlighting for RISCV (PR #65853)

[Yingwei Zheng via cfe-commits]

=?utf-8?q?Björn_Schäpers?= <bjoern at hazardy.de>,Mehdi Amini
 <joker.eph at gmail.com>,Vitaly Buka <vitalybuka at google.com>,Vitaly Buka
 <vitalybuka at google.com>,Vitaly Buka <vitalybuka at google.com>,Mehdi Amini
 <joker.eph at gmail.com>,Shilei Tian <i at tianshilei.me>,"Kazushi (Jam) Marukawa"
 <marukawa at nec.com>,Fabian Mora <fmora.dev at gmail.com>,Kazushi Marukawa
 <marukawa at nec.com>,Jonas Devlieghere <jonas at devlieghere.com>,Jan Svoboda
 <jan_svoboda at apple.com>,Jan Svoboda <jan_svoboda at apple.com>,Alex Brachet
 <abrachet at google.com>,Jan Svoboda <jan_svoboda at apple.com>,Jan Svoboda
 <jan_svoboda at apple.com>,Jan Svoboda <jan_svoboda at apple.com>,Jan Svoboda
 <jan_svoboda at apple.com>,Jan Svoboda <jan_svoboda at apple.com>,Fangrui Song
 <i at maskray.me>,Matt Arsenault <Matthew.Arsenault at amd.com>,Younan Zhang
 <zyn7109 at gmail.com>,Brad Smith <brad at comstyle.com>,Christian Sigg
 <chsigg at users.noreply.github.com>,David Green <david.green at arm.com>,David
 Green <david.green at arm.com>,Piotr Zegar <me at piotrzegar.pl>,Ignat Loskutov
 <ignat.loskutov at gmail.com>,Alex Brachet <abrachet at google.com>,Congcong Cai
 <congcongcai0907 at 163.com>,Congcong Cai <congcongcai0907 at 163.com>,Jan Svoboda
 <jan_svoboda at apple.com>,Jan Svoboda <jan_svoboda at apple.com>,Yingwei Zheng
 <dtcxzyw2333 at gmail.com>,Simon Pilgrim <llvm-dev at redking.me.uk>,Piotr Zegar
 <me at piotrzegar.pl>,Jan Svoboda <jan_svoboda at apple.com>,Jan Svoboda
 <jan_svoboda at apple.com>,Mark de Wever <koraq at xs4all.nl>,Jan Svoboda
 <jan_svoboda at apple.com>,Jay Foad <jay.foad at amd.com>,Yingwei Zheng
 <dtcxzyw2333 at gmail.com>,Yingwei Zheng <dtcxzyw2333 at gmail.com>,Simon Pilgrim
 <llvm-dev at redking.me.uk>,Yingwei Zheng <dtcxzyw2333 at gmail.com>,Fangrui Song
 <i at maskray.me>,Owen Pan <owenpiano at gmail.com>,Billy Laws <blaws05 at gmail.com>,Fangrui
 Song <i at maskray.me>,Tianlan Zhou <bobby825 at 126.com>,Yingwei Zheng
 <dtcxzyw2333 at gmail.com>


https://github.com/dtcxzyw review_requested https://github.com/llvm/llvm-project/pull/65853