WIP: Escaping characters sent to TTS

[tlhunter]

• Fixes Project probably has security vulnerabilities #90
• Fixes It needs to escape text. #93
• SEMVER: This is a MAJOR change, but since pre 1.0, can be a MINOR

This change highlights the need for a real test suite :(

[JamieVangeysel]

You shouldn't replace [ and ] since they are used on macOS, for example, Hello world! [[rate 400]] This text is spoken rapidly. [[volm 0.4]] This text is spoken very quiet[[rset]].
See: Apple SpeechSynthesisProgrammingGuide Table 3-1