add query expression for word-boundary and use it in symbols and project-symbols

[t9md]

Fix #169
Related #50

What will change

Add query expression which specify word-boundary(\b) search.

Here is how query translated

  # Translate
  # - ">word<" to "\bword\b"
  # - ">word" to "\bword"
  # - "word<" to "word\b"
  if /^>./.test(pattern)

If \b is meaningless(e.g. >=), it don't add \b, but remove > or < for consistency.

NOTE: I also evaluated not-trim starting > so that user don't need to search by >>= for search >= literal.
But it was not obvious when > is removed or not removed, which make user learning difficult, so avoided this approach.

Auto enable word boundary query when symbols and project-symbols invoked by by-current-word command

Purpose: To make quick previewing by symbols-by-current-word or project-symbols-by-current-word further useful.

Before: Problematic situation

1. Place cursor on @refresh function and invoke
2. narrow:symbols-by-current-word: Previewing unwanted function(multiple symbols which contains refresh)
3. narrow:project-symbols-by-current-word: Previewing unwanted function(multiple symbols which contains refresh)

After: Find target thanks to >refresh< query.

1. Place cursor on @refresh function and invoke
2. narrow:symbols-by-current-word: Previewing single preview function.
3. narrow:project-symbols-by-current-word: Previewing single preview function.