Added xml comment toggle from Saphia Thach, made more generic and use…

[slimjimsoftware]

Added xml comment toggle from Saphia Thach, made more generic and used in block / line comments

This enables IntelliJ style XML comment / uncomment (if an existing XML comment is found between the first and last rows of the block / line comment it will be escaped before commenting and / un-escaped after uncommenting.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[codecov]

Codecov Report

Merging #4113 into master will decrease coverage by <.01%.
The diff coverage is 69.76%.

@@            Coverage Diff             @@
##           master    #4113      +/-   ##
==========================================
- Coverage   70.32%   70.32%   -0.01%     
==========================================
  Files         519      519              
  Lines       50890    50933      +43     
  Branches     9588     9598      +10     
==========================================
+ Hits        35787    35817      +30     
- Misses      15103    15116      +13

Impacted Files	Coverage Δ
lib/ace/mode/text.js	73.49% <69.76%> (-0.67%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update f333862...a26090b. Read the comment docs.