v0.2.0: documentation and tools to create MSA contexts

What's Changed

Major:

• Support for MSA contexts and .aligned.pqt format by @wukevin in #109

Minor:

• document envvar CHAI_DOWNLOADS_DIR by @arogozhnikov in #115
• fix race conditions during downloads by @arogozhnikov in #114
• Update technical report link by @jackdent in #105 #112
• resize image to have proper h/w ratio on all devices by @arogozhnikov in #106
• Add bibtex record for citation by @arogozhnikov in #107 #108
• remove redundant check by @arogozhnikov in #116
• Correct grammar in README by @jackdent in #119
• bump version by @arogozhnikov in #120

Full Changelog: v0.1.0...v0.2.0