feat(gatsby-remark-prismjs): syntax highlighting inside diffs (gatsby…

…js#26525)

* feat(gatsby-remark-prismjs): syntax highlighting inside diffs

added support for syntax highlighting inside diffs using diff-xxxx
pattern as language identifier

✅ Closes: gatsbyjs#20630

* add minimal documentation about `diff-[language]`

* \w means [a-zA-Z0-9_] so we can drop \d ([0-9]) as it's already covered

* add top level test to also cover regex part

Co-authored-by: Michal Piechowiak <misiek.piechowiak@gmail.com>

yarn.lock

@@ -1851,12 +1851,7 @@
     "@types/node" "*"
     form-data "^3.0.0"
 
-"@types/node@*":
-  version "14.6.4"
-  resolved "https://registry.yarnpkg.com/@types/node/-/node-14.6.4.tgz#a145cc0bb14ef9c4777361b7bbafa5cf8e3acb5a"
-  integrity sha512-Wk7nG1JSaMfMpoMJDKUsWYugliB2Vy55pdjLpmLixeyMi7HizW2I/9QoxsPCkXl3dO+ZOVqPumKaDUv5zJu2uQ==
-
-"@types/node@^8.5.7":
+"@types/node@*", "@types/node@^8.5.7":
   version "8.10.63"
   resolved "https://registry.yarnpkg.com/@types/node/-/node-8.10.63.tgz#f86775d576bc07a2992da244f41c23d3ba66d402"
   integrity sha512-g+nSkeHFDd2WOQChfmy9SAXLywT47WZBrGS/NC5ym5PJ8c8RC6l4pbGaUW/X0+eZJnXw6/AVNEouXWhV4iz72Q==