Removes `clipboardy` dependency

• documents 'copyToClipboardCommand' configuration item 8394efc
• clipboard-util.ts: attempts to use the configured clipboard command if one is found 8eb82de
• config-util.ts: adds copyToClipboardCommand option 8f37b8c
• test string to command array will return an empty array when given a blank string 3d55c1f
• (package.json) removes dev dependency on 'ts-node' 031a5e6
• (package.json) removes dependency on 'clipboardy' e704083
• replaces clipboardy usages with new util function e6b5442
• adds clipboard-util.ts to handle copying to clipboard in MacOS and Linux e083785
• npm audit fix 194049b
• uses key definitions instead of string literals 0679c3f
• adds keys-def.ts: consolidates all reserved keys into a single spot b662700
• rename variable: KEY_NAV_INTERVAL -> NAV_INTERVAL 1d53f3a
• (config-util.ts) simplifies code and prints a nice .jack.json file ba7494a

v1.2.6...v1.3.0