Fixed spelling and made the acceptance criteria for new items clearer

CONTRIBUTING.md

@@ -2,24 +2,26 @@
 
 Unfortunately, not every library/tool/framework can be considered. The aim of the list is to provide a concise list of noteworthy modern software. This means that suggested software is either
 
-(a) widely recommended and used regardless of your personal opinion
+(a) widely recommended regardless of personal opinion
 
 (b) highly discussed in the community due to its innovative nature
 
-(b) absolutely unique in its approach and function
+(c) absolutely unique in its approach and function
 
-Self-promotion is frowned upon and will be reviewed critically but the suggestion will of course be approved if the criteria match.
+(d) a niche product that fills a gap
+
+Self-promotion is frowned upon and will be reviewed critically but the suggestion will of course be approved if they criteria match.
 
 If a certain entry does not get accepted, you should first look if there has been a discussion before. These discussions are in the issue section and normally marked with the question tag. If there hasn't been such a topic, you are free to create a new issue tagged as question.
 
 
-Furthermore, please ensure your pull request follows the following guidlines:
+Furthermore, please ensure your pull request follows the following guidelines:
 
 * Please search previous suggestions before making a new one, as yours may be a duplicate.
 * Please make an individual pull request for each suggestion.
 * Use the following format for libraries: \[LIBRARY\]\(LINK\) - DESCRIPTION.
 * Entries should be sorted in ascending alphabetical order, i.e. a to z.
-* New categories, or improvements to the existing categorisation are welcome.
+* New categories, or improvements to the existing categorization are welcome.
 * Keep descriptions short, simple and unbiased. 
 * End all descriptions with a full stop/period.
 * Check your spelling and grammar.