Project and Context case sensitive

[clach04]

The spec is very clear on case sensitivity for:

• Priority - https://github.com/todotxt/todo.txt/blob/master/README.md?plain=1#L87
• Completion status - https://github.com/todotxt/todo.txt/blob/master/README.md?plain=1#L156

it does not mention case for Project tags and Context Tags, however I think it is implied to be case sensitive and https://github.com/todotxt/todo.txt-cli/blob/master/todo.sh#L1031 is explicitly case sensitive when searching

In the Android apps I've experimented with, Project and Context are both case sensitive.

Any objections to documenting this explicitly?