fix: emoji context (#1190)

| [![PR App][icn]][demo] | RM-13827 |
| :--------------------: | :------: |

## 🧰 Changes

Prevents rendering gemoji's unless preceded by a space or at the start
of a line.

## 🧬 QA & Testing

- [Broken on production][prod].
- [Working in this PR app][demo].

[demo]: https://markdown-pr-PR_NUMBER.herokuapp.com
[prod]: https://SUBDOMAIN.readme.io
[icn]:
https://user-images.githubusercontent.com/886627/160426047-1bee9488-305a-4145-bb2b-09d8b757d38a.svg

**BREAKING CHANGE**: Changes how emoji's are parsed in markdown.

Author: kellyjosephprice

__tests__/parsers/gemoji.test.ts

@@ -61,4 +61,12 @@ describe('gemoji parser', () => {
 
     expect(mdast(markdown).children[0].children[0].value).toMatch(/:unknown-emoji:/);
   });
+
+  const beforeTests = ['letter', '1', '.', ':', "'", '!', '?', ',', ';', '(', '[', ')', ']', '}'];
+
+  it.each(beforeTests)('should not render an emoji following a "%s"', string => {
+    const tree = mdast(`${string}:joy:`);
+
+    expect(tree.children[0].children[0].value).toBe(`${string}:joy:`);
+  });
 });

processor/transform/gemoji+.ts

@@ -6,7 +6,7 @@ import { findAndReplace } from 'mdast-util-find-and-replace';
 import { NodeTypes } from '../../enums';
 import Owlmoji from '../../lib/owlmoji';
 
-const regex = /:(?<name>\+1|[-\w]+):/g;
+const regex = /(?<=^|\s):(?<name>\+1|[-\w]+):/g;
 
 const gemojiReplacer = (_, name: string) => {
   switch (Owlmoji.kind(name)) {