[clang-tidy][docs] Mention in docs that we currently do not accept checks for MISRA/AUTOSAR due to legal/license reasons

[vbvictor]

Based on #160745 (comment) from @carlosgalvezp (see comment for detailed info), we should write that checks that directly reference MISRA/AUTOSAR guidelines are prohibited but generic checks without direct links are allowed.

[llvmbot]

@llvm/issue-subscribers-clang-tidy

Author: Baranov Victor (vbvictor)

Based on https://github.com//pull/160745#issuecomment-3337134160 from @carlosgalvezp (see comment for detailed info), we should write that checks that directly reference MISRA/AUTOSAR guidelines are prohibited but generic checks without direct links are allowed.